Communiqué. The Challenges of Testing For and Diagnosing Porphyrias

Transcription

1 Communiqué November 2002 AVolume 27 Number 11 Features The Challenges of Testing For and Diagnosing Porphyrias Inside Ask Us Abstracts of Interest Calendar Test Updates: Cobalt Serum Specimen Correction Metanephrine/ Normetanephrine Test Adds Hypertensive Reference Range Trichophyton Test Title Change W Xanthine, Hypoxanthine, Purine, and Pyrimidine Move to LC-MS/MS New Test Announcements Chlamydia trachomatis by Nucleic Acid Amplification C trachomatis/n gonorrhoeae by Nucleic Acid Amplification Hereditary Pancreatitis, Blood Neisseria gonorrhoeae by Nucleic Acid Amplification Postmortem Screening, Bile/Blood Spots Testosterone, Total and Bioavailable, Serum Communiqué Stabile Building 150 Third Street SW Rochester, Minnesota communique@mayo.edu A M a y o R e f e r e n c e S e r v i c e s P u b l i c a t i o n The Challenges of Testing For and Diagnosing Porphyrias The porphyrias are a group of inborn errors of metabolism resulting from defects in the heme biosynthetic pathway. Enzymatic deficiencies resulting in the accumulation and excretion of intermediary metabolites cause characteristic clinical manifestations, which include neurological and psychological symptoms and/or cutaneous photosensitivity. Although these disorders have genetic causes, environmental factors may exacerbate symptoms, which significantly impacts the severity and course of disease. Early diagnosis coupled with education and counseling of the patient regarding the nature of the disease and avoidance of precipitating factors are important for successful management. Photo 1. This patient s hands demonstrate the cutaneous photosensitivity that is associated with the cutaneous, nonacute porphyrias. The chronic nature of the lesion results in scarring. Heme Biosynthetic Pathway The heme biosynthetic pathway (Figure 1, page 3) consists of 8 enzymes. The first and last 3 enzymes in the pathway are localized in the mitochondria, and the intermediate enzymes function in the cytosol. The formation of heme begins with the condensation of glycine and succinyl-coenzyme A to 5-aminolevulinic acid. (5-aminolevulinic acid is also referred to as deltaaminolevulinic acid, δ-aminolevulinic acid, and aminolevulinic acid. It will be abbreviated as ALA in this issue.) This is followed by a series of enzymatic reactions that convert ALA to porphobilinogen (PBG) and then to the various porphyrinogens. Finally, iron is inserted into protoporphyrin by the enzyme ferrochelatase, forming heme. The production of heme, a metalloporphyrin containing iron, occurs in all metabolically active cells. The majority is formed in erythropoietic cells where it is incorporated in hemoglobin. Hepatic tissue also produces a significant amount for use in myoglobin and various heme-containing enzymes including cytochromes, catalases, and peroxidases. Heme that is not immediately utilized in a protein complex is metabolized to bile pigments. Each porphyria is caused by a specific enzyme deficiency involved in the heme biosynthetic pathway. Consequently, clinical symptomology results from the accumulation of porphyrinogens, porphyrins, and their precursors, which are formed prior to the enzyme defect. Depending upon the primary site of accumulation, porphyrias have been classified as either erythropoietic or hepatic. Cutaneous, Nonacute Porphyrias The nonacute porphyrias include porphyria cutanea tarda, hepatoerythropoietic porphyria, erythropoietic protoporphyria, and congenital erythropoietic porphyria. These disorders are characterized by chronic dermatologic symptoms. While cutaneous photosensitivity is a common feature among the nonacute porphyrias, other associated clinical and biochemical features, inheritance patterns, and medical management remain unique for each. (See Photos 1 and 2.)

2 epidermis papillae vessels thickened basement membrane zone dermis Photo 2. This slide shows the thickened vessels, visible as bright-green donut shapes, and the thickened basement membrane zone that are characteristic of a diagnosis of porphyria. Porphyria Cutanea Tarda Porphyria cutanea tarda (PCT) is the most common porphyria and is most amenable to treatment. It is unique in that it may be an acquired (sporadic, type I) or an inherited (familial, types II and III) condition. About 75% of patients have type I PCT. In these cases, symptoms are precipitated by complications from liver diseases, such as hepatitis C and hereditary hemochromatosis, or by environmental exposures including certain medications, estrogens, alcohol abuse, iron overload, smoking, and occupational exposures to polychlorinated cyclic hydrocarbons. Historically, outbreaks have been caused by toxic exposure to certain organic chemicals. Observed less commonly is familial PCT. It is estimated that 25% of patients are affected with this autosomal dominant condition. In type II PCT, uroporphyrinogen decarboxylase activity is approximately 50% of normal in all tissues, while in type III the enzyme is deficient only in hepatic cells. In the absence of a positive family history, type III PCT is virtually indistinguishable from the sporadic form. PCT is characterized by photosensitivity and skin fragility. Patients experience blistering lesions in sun-exposed areas resulting in cutaneous thickening and scarring. The face, neck, forearms, and backs of hands are areas most often affected. Minor trauma may also trigger lesions. Twothirds of patients experience hypertrichosis (excessive hair growth) on the face, and less frequently on the ears and arms. Approximately half of individuals with PCT have hyperpigmentation in sun-exposed areas, while one-third of patients develop patches of alopecia as a result of scarring from large blisters on the scalp. In most cases, patients exhibit abnormal liver function tests. Long-term complications include an increased risk for hepatic cirrhosis and hepatocellular carcinoma. Iron overload may occur in association with PCT. Hemosiderosis is usually mild or moderate, although can be severe. Interestingly, patients with hereditary hemochromatosis are more likely to experience symptoms of PCT than individuals in the general population. PCT is observed more frequently in males than in females. It is hypothesized that this may be related to varying levels of alcohol consumption and other environmental exposures between men and women. A second theory postulates that menses may provide a level of protection for women as it acts as a form of phlebotomy, which is an effective treatment for PCT. The diagnosis of PCT is easily established through elevations of uroporphyrin and heptacarboxylporphyrin in 24-hour urine porphyrins (#8562 Porphyrins, Quantitative, Urine) and uroporphyrin in plasma (#8733 Porphyrins, Fractionation, Plasma). In PCT urine uroporphyrin levels are typically elevated to at least 4 times the upper limit of normal, but concentrations may reach as high as 250 times the upper limit of normal. In general, heptacarboxylporphyrin is at least 25% of the uroporphyrin value. (Elevated uroporphyrin without a concomitant elevation of heptacarboxylporphyrin is often observed in the acute porphyrias, rather than PCT.) A urine uroporphyrin level twice the upper limit of normal is suspicious for PCT and justifies further investigation. Thus, subsequent plasma and fecal (#81652 Porphyrins, Feces) porphyrin analyses and a repeat urine porphyrin analysis are recommended, particularly if symptoms develop or continue to persist. Plasma testing in cases of PCT demonstrates plasma porphyrin levels that are typically elevated at least 5 times the upper limit of normal. Conversely, mild elevations in plasma levels are associated with renal disease. Sporadic versus familial PCT can be distinguished by enzyme analysis (#8599 Uroporphyrinogen Decarboxylase [Upg D], Erythrocytes) and eliciting a thorough family history. Enzymatic assay is not an appropriate first-level assay as the majority of cases are sporadic and the enzyme exhibits normal activity in these cases. The cutaneous symptoms of PCT are more amenable to treatments than are similar complications seen in other forms of porphyria. Phlebotomy therapy and low-dose chloroquine, an antimalarial drug, result in complete 2 11/02

3 Figure 1. Heme Biosynthetic Pathway 11/02 3

4 remission of skin lesions in most cases. Phlebotomy produces remission by gradually reducing the hepatic iron overload. Serial serum ferritin (#8689 Ferritin, Serum) and plasma porphyrin (#8733 Porphyrins, Fractionation, Plasma) levels are useful in evaluating the efficacy of treatment. Low-dose chloroquine treatments have proven valuable as the drug complexes with excess porphyrins, promoting excretion. However, these therapies should only be initiated following biochemical confirmation of the clinical diagnosis, as they are not useful in other porphyrias presenting with cutaneous symptoms. Occurrences of dermatologic complications can be minimized through elimination or reduction of precipitating factors via sun avoidance and use of sunscreen, abstaining from alcohol, discontinuing estrogen therapy, or treatment of an underlying liver disorder. Even with these treatments, long-term follow-up is important for all patients as a means of monitoring for relapse through urine (#8562 Porphyrins, Quantitative, Urine) and plasma (#8733 Porphyrins, Fractionation, Plasma) porphyrin analysis, and for the management of any concomitant liver disease. Generally, PCT is not attributable to a single causal factor. Even in familial PCT, most patients have identifiable risk factors in addition to the hereditary enzyme deficiency. Therefore, all patients presenting with PCT should be evaluated for multiple risk factors, including testing for hepatitis C virus and screening for hemochromatosis, and treated accordingly. Hepatoerythropoietic Porphyria Hepatoerythropoietic porphyria (HEP) is a severe porphyria due to markedly deficient uroporphyrinogen decarboxylase activity or homozygous PCT. Onset of this rare porphyria usually occurs in infancy or childhood, although cases presenting in adulthood have been described. Patients experience severe photosensitivity leading to blistering lesions and scarring. Other complications include pink or red urine, hypertrichosis, erythrodontia (reddish discoloration of the teeth), hepatosplenomegaly, and hemolytic anemia. Treatment is limited to sun avoidance and the use of sunscreens. Erythropoietic Protoporphyria A deficiency of the enzyme ferrochelatase is observed in patients with erythropoietic protoporphyria (EPP). EPP is an autosomal dominant disorder with reduced penetrance. Only about 10% of individuals with an enzyme deficiency develop clinical symptoms. While onset usually occurs before 10 years of age, clinical presentation may occur during childhood or adulthood. Individuals with EPP are sensitive to most of the visible light spectrum. Such exposure causes burning, itching, and painful erythema and edema that can develop within minutes. Blistering and scarring is less common than in other dermatologic porphyrias. Repeated exposures may result in chronic changes giving the skin a waxy, thickened appearance with faint linear scars. Cutaneous photosensitivity is exacerbated in the spring and summer when exposure to sunlight is more likely. Patients are at an increased risk to develop hemolytic anemia. Gallstone formation is common, and some individuals with EPP experience mild hypertriglyceridemia. Liver dysfunction and hepatic failure are observed in up to 20% and less than 5% of patients, respectively. Patients with EPP accumulate protoporphyrin in erythrocytes, plasma, and feces. Other heme pathway intermediates do not accumulate, and protoporphyrin is not soluble in urine. For these reasons, urinary porphyrin, ALA, and PBG are not useful diagnostic tools for this disorder. When a diagnosis of EPP is suspected, the tests of choice are total porphyrins and protoporphyrin fractionation (#8536 Porphyrins, Total, Erythrocytes or #8739 Protoporphyrins, Fractionation, Erythrocytes) in erythrocytes. Unaffected individuals have approximately 60 µg/dl total protoporphyrin with approximately 85% being zinc-complexed and 15% or less free protoporphyrin. In EPP patients, the total erythrocyte protoporphyrin is significantly increased with values usually >200 µg/dl. Some patients have been observed with total protoporphyrin exceeding 1000 µg/dl. When the total protoporphyrin is fractionated, EPP patients exhibit more free than zinccomplexed protoporphyrin. However, iron deficiency, lead intoxication, or in very rare cases variegate porphyria should be suspected in patients who exhibit total protoporphyrin in excess of 200 µg/dl but have more zinc-complexed than free protoporphyrin. Although EPP is the third most common porphyria, treatment options are limited. Sun avoidance is essential, and protective clothing and sunscreen are recommended. Oral administration of beta-carotene allows for increased tolerance to sunlight in most patients. Although there are no other known precipitating factors, many advocate the avoidance of drugs and other elements that may induce crises in the acute porphyrias. Liver transplantation is an option for 4 11/02

5 the minority of patients who experience hepatic failure. However, this is not a cure as the excessive porphyrins are produced in the erythropoietic cells. Congenital Erythropoietic Porphyria Congenital erythropoietic porphyria (CEP), also known as Gunther disease, is an extremely rare and severe porphyria. It is an autosomal recessive condition resulting from markedly deficient uroporphyrinogen III cosynthase activity. Although the disorder typically manifests in early infancy, variability in the age of onset and severity are thought to be related to the level of residual enzyme activity. Prenatal manifestation of CEP presents as nonimmune hydrops fetalis (abnormal accumulation of serous fluid in fetal tissues) due to severe hemolytic anemia, whereas only cutaneous lesions are observed in the mildest cases manifesting in adulthood. Clinically, the majority of patients with CEP present in infancy with dermatological complications including photosensitivity, blistering, erythrodontia, and hypertrichosis. The skin may become thickened, and areas of hypopigmentation and hyperpigmentation are observed. Recurrent blistering and secondary infection may lead to significant scarring and mutilation. Exposure to sunlight and other sources of ultraviolet light exacerbate the severity of the cutaneous symptoms. In fact, some patients present at birth when undergoing phototherapy for hyperbilirubinemia. Ophthalmological findings include keratoconjunctivitis (inflammation of the conjunctiva and of the cornea), ulcerations, cataracts, and corneal scarring that can lead to blindness. Hemolytic anemia and other hematologic abnormalities accompanied by splenomegaly are common. To compensate for this, increased metabolic activity and expansion of the bone marrow may lead to pathologic fractures and vertebral compression or collapse. Many patients develop porphyrin-rich gallstones. Pink or reddish-brown urine is often observed as a result of the increased excretion of urinary porphyrins. Moreover, severely affected individuals exhibit growth and cognitive developmental delays and a decreased lifespan. A combination of urine (#8562 Porphyrins, Quantitative, Urine), erythrocyte (#8536 Porphyrins, Total, Erythrocytes and #8735 Porphyrins, Fractionation, Erythrocytes), and fecal (#81652 Porphyrins, Feces) porphyrin analyses can diagnose CEP. Porphyrins in urine are predominantly the I series isomers of uroporphyrin and coproporphyrin. Patients with CEP show elevated erythrocyte porphyrins consisting primarily of uroporphyrin I. Coproporphyrin I is detected in feces. The diagnosis of CEP should be confirmed by erythrocyte uroporphyrinogen III cosynthase enzyme analysis (#80288 Uroporphyrinogen III Synthase (Co- Synthase) (Upg III S), Erythrocytes). Enzyme analysis must be performed prior to blood transfusion to achieve the most accurate results. Furthermore, uroporphyrinogen III cosynthase testing is not useful for carrier testing, as CEP heterozygotes cannot be distinguished from unaffected individuals. Molecular studies are currently not available on a clinical basis, but may be obtained in a research setting. Treatment for CEP requires protection from ultraviolet light to reduce dermatological and ophthalmological complications. To minimize the risk of mutilation, secondary infections must be treated immediately. Blood transfusions and splenectomy are beneficial in some cases by decreasing porphyrin production and limiting hemolytic anemia. Allogenic bone marrow transplantation has proven curative for a handful of patients. However, this therapy carries a considerable risk for mortality. Acute Porphyrias The acute porphyrias include acute intermittent porphyria, variegate porphyria, hereditary coproporphyria, and 5-aminolevulinic acid dehydratase deficiency. Episodic neurovisceral symptoms that can be life threatening characterize the acute porphyrias. Cutaneous features also may manifest in some patients. Acute episodes can be precipitated by both endogenous and exogenous factors. These factors and clinical management are similar for all types of the acute porphyrias and are discussed following the clinical descriptions of each. Acute Intermittent Porphyria Acute intermittent porphyria (AIP), the second most common porphyria, results from a deficiency in the enzyme porphobilinogen deaminase (PBGD), also called uroporphyrinogen I synthase or hydroxymethylbilane synthase. AIP is aptly named for the intermittent episodes in which patients experience acute neuropathic symptoms. These acute episodes are potentially lifethreatening, highly variable, and although usually short in duration, may last from a few days to several months. 11/02 5

6 AIP rarely presents prior to puberty, with onset most commonly between ages 20 and 40. It is characterized by episodes of acute neuropathic symptoms. Most patients, approximately 95%, experience severe abdominal pain, often in conjunction with nausea, vomiting, and constipation. Peripheral neuropathy is common. However, given the extensive list of differential diagnoses for patients experiencing peripheral neuropathy, testing for AIP in the absence of abdominal pain rarely identifies AIP patients and is not recommended. Patients frequently display psychiatric symptoms presenting in the form of psychotic episodes, depression, and anxiety. Other features of an acute attack include circulatory disturbances such as hypertension and tachycardia. Dysuria and urinary retention, sometimes requiring catheterization, may be seen. Less frequently, patients may experience seizures, respiratory paralysis, fever, and diarrhea. Given the highly variable and nonspecific nature of the neurovisceral symptoms observed in AIP attacks, the condition is often overlooked in the clinical setting. Unfortunately, appropriate laboratory investigations are often not conducted, and many patients are misdiagnosed or become incorrectly labeled as narcotic seeking. This leads to a potentially life-threatening situation as patients continue to be at risk for an acute attack. Inheritance of AIP occurs in an autosomal dominant manner with reduced penetrance. Approximately 10-20% of individuals with a PBGD enzyme deficiency will become symptomatic during their lifetime, although some recent studies have questioned this low penetrance rate. 1,2 While the vast majority of patients will never exhibit symptoms, the identification of asymptomatic, affected individuals in families with known AIP is crucial. The diagnosis of asymptomatic patients allows for the avoidance of precipitating factors, thereby minimizing the risk of a life-threatening porphyric attack. With respect to the initial diagnosis of symptomatic patients believed to be in an acute AIP crisis, urine porphyrins (#8562 Porphyrins, Quantitative, Urine), ALA (#8406 Aminolevulinic Acid [ALA], Urine), and PBG (#82068 Porphobilinogen, Quantitative, Random, Urine) should be analyzed. Substantial financial savings and improvement in the appropriateness of testing can be attained by following our suggested testing strategies for the acute porphyrias (see Table 1). 5 This will ensure that another acute porphyria, with features similar to AIP, is not missed. PBGD (#9625 Aminolevulinic Acid Dehydratase [ALA-D] and Porphobilinogen Deaminase [Pbg-D] (Uroporphyrinogen Synthase [UpgS]), Erythrocytes) enzyme activity should be evaluated either in conjunction with these urine analyses or preferably in a stepwise fashion when indicated, based upon the urine studies. Identification of asymptomatic, affected family members, including children, is possible and requires either biochemical or molecular analysis. However, molecular testing is not readily available on a clinical basis at this time. Urinary ALA and PBG values are method dependent and can vary by institution. Some experts believe that these analytes will never fall within the normal range in asymptomatic, affected individuals, whereas others argue that these values can normalize in such patients. With the assays available through Mayo Medical Laboratories (MML), elevated urinary ALA and PBG values have been observed in asymptomatic individuals in whom AIP status was previously unknown. Provision of clinical information and reason for referral is important for accurate result interpretation. Regarding the diagnosis of asymptomatic infants and children, there is evidence that PBGD activity fluctuates considerably during the first 9-12 months of life; therefore, enzyme analysis should be performed after 1 year of age. In some cases, it is helpful to perform PBGD analysis of known affected family members when attempting to rule in/out AIP in asymptomatic relatives. Given that up to 10% of asymptomatic individuals with AIP will have a normal PBGD result, the urine assays are important diagnostic tools. Variegate Porphyria Variegate porphyria (VP) is an autosomal dominant acute porphyria that results from a reduction in the activity of protoporphyrinogen oxidase activity. VP is pan-ethnic, although high prevalence is reported in South Africa (3/1000 individuals) and Finland. Reduced penetrance is observed and symptoms very rarely present before puberty. Clinical presentation of VP is similar to other acute porphyrias, with symptoms including abdominal pain, vomiting, neuropathies, and psychiatric sequelae. However, cutaneous involvement is usually more pronounced. In fact, dermatologic manifestations in VP are very similar to those seen in PCT and include blistering, hyperpigmentation, and hypertrichosis of sun-exposed areas. Moreover, while neuropathic symptoms appear only during acute crisis, photosensitivity remains a chronic symptom. In rare instances, homozygous VP, with marked deficiency of protoporphyrinogen oxidase enzyme 6 11/02

7 activity, has been described. Patients typically present in early childhood with photosensitivity resulting in severe cutaneous manifestations, neurologic symptoms including seizures, and developmental delay. The diagnosis of VP relies upon porphyrin analysis in urine (#8562 Porphyrins, Quantitative, Urine) and feces (#81652 Porphyrins, Feces), as enzyme and molecular analysis of protoporphyrinogen oxidase are not readily available on a clinical basis. Depending upon whether the patient is experiencing an acute crisis or is asymptomatic, urine coproporphyrin, ALA, and PBG values are elevated to varying degrees. Values may be as high as times normal during acute crises but may be normal or only mildly elevated between attacks. During crises, fecal porphyrin analysis shows coproporphyrin levels are, at a minimum, double with a coproporphyrin III to coproporphyrin I ratio in the 3-10 range (normal ratio <1.2). Additionally, fecal protoporphyrin IX is elevated to a greater extent than coproporphyrin. In asymptomatic patients, fecal porphyrins typically remain elevated. Hereditary Coproporphyria A reduction of coproporphyrinogen oxidase activity results in hereditary coproporphyria (HCP), an autosomal dominant condition. While exact prevalence is unknown, HCP is one of the least common of the acute porphyrias. Clinical penetrance is low, and symptoms very rarely present before puberty. Clinical manifestations of HCP are predominantly neurovisceral and closely resemble those of other acute porphyrias. However, about one third of cases exhibit photosensitivity similar to PCT and VP. Those HCP patients not presenting with dermatologic findings are clinically indistinguishable from patients with AIP and VP. Consequently, biochemical analysis is essential for correct diagnosis. Harderoporphyria, a very rare variant of HCP, is inherited in a homozygous manner and very low residual enzyme activity is observed. Features include neonatal hemolytic anemia and cutaneous involvement. Neither coproporphyrinogen oxidase enzyme nor molecular analyses are clinically available at this time. The biochemical hallmark of HCP is hyperexcretion of coproporphyrin in the urine (#8562 Porphyrins, Quantitative, Urine) and feces (#81652 Porphyrins, Feces) at levels similar to that observed in VP. However, in HCP, the fecal coproporphyrin III to coproporphyrin I ratio is in the range (normal ratio <1.2) and protoporphyrin is typically not elevated. Thus, fecal porphyrin analysis allows for the distinction between HCP from VP and AIP. ALA Dehydratase Deficiency 5-ALA dehydratase deficiency porphyria (ALAD) is a rare, autosomal recessive variant of the acute porphyrias that results from homozygous or compound heterozygous deficiency of 5-ALA dehydratase. Clinical manifestations of ALAD are predominantly neuropathic and include abdominal pain, vomiting, and pain in the extremities. The age of onset and degree of severity are highly variable among the few reported patients. Heterozygote carriers of ALAD may be at increased risk for developing an acute porphyric episode following toxic exposure to lead or a variety of other chemicals. ALAD can be differentiated from other acute porphyries by normal urinary PBG (#82068 Porphobilinogen, Quantitative, Random, Urine) in the presence of significantly elevated ALA (#8406 Aminolevulinic Acid [ALA], Urine) and markedly decreased ALA dehydratase activity. Enzyme assay for 5-ALA dehydratase (#9625 Aminolevulinic Acid Dehydratase [ALA-D] and Porphobilinogen Deaminase [Pbg-D] (Uroporphyrinogen Synthase [UpgS]), Erythrocytes) is clinically available and all patients reported to date show <5% of normal 5-ALA dehydratase in erythrocytes. 3 There is little documented experience in the treatment of ALAD. The current management approach is similar to that for other acute porphyrias, as emphasis is placed on the prevention of acute attacks. Lead intoxication can also produce elevated ALA with normal PBG. Therefore, whole blood lead analysis (#15070 Lead with Demographics, Blood) should be pursued in such crises to rule out that possibility. Precipitating Factors for Acute Porphyrias There is considerable evidence that acute crises are precipitated by endogenous and exogenous factors. These include hormonal changes, drugs and alcohol, nutritional factors, stress, and infections, which potentially allow for the upregulation of the heme biosynthetic pathway. Consequently, the partial deficiency in PBGD becomes rate limiting, allowing for the buildup of PBG and ALA, culminating in an acute crisis. Endocrine factors are believed to play a major role in the induction of AIP in some patients. Women are more likely to exhibit clinical disease. Furthermore, acute 11/02 7

8 attacks rarely occur before puberty, and attack frequency and severity decline after menopause. Interestingly, a subset of female patients experience regular, cyclical, exacerbations of disease in conjunction with menses. A variety of drugs, including alcohol, have been implicated in the induction of acute porphyric attacks. There is consensus regarding the use and safety of many common medications in patients with AIP. Other drugs are not as well understood. Some commonly used drugs, which have been classified as safe or unsafe for use by patients with an acute porphyria, are listed in Table 1. More extensive lists, including drugs whose safety is still in question, are available elsewhere. 3 Medications previously established as safe should be used whenever possible in patients with asymptomatic or symptomatic AIP. Nutritional status, in particular decreased caloric intake, has been shown to induce the onset of an acute attack. Intercurrent illnesses and surgery exhibit a causal relationship, possibly due to increased energy requirements during these times. Additionally, psychological stress has been reported to contribute to AIP symptomology, though the underlying mechanisms are not understood. Precipitating factors likely act in an additive fashion, and the trigger(s) of a particular crisis, cannot always be ascertained. Table 1. Medications and the acute porphyrias Treatment for Acute Porphyrias Hospitalization is often necessary for the treatment of acute attacks. Crises are treated with increased carbohydrate intake that may occur via intravenous administration. Heme (hematin or heme arginate) therapy allows for the excretion of ALA and PBG. Efficacy is compromised if heme therapy is delayed, so treatment should commence as soon as possible after the onset of a crisis. Symptomatic treatment includes frequent doses of analgesics to control pain, and phenothiazines may be administered to control nausea, vomiting, and anxiety. Given that pain tends to be severe, narcotics are typically the analgesia of choice, as nonnarcotic agents are usually inadequate. Treatment for asymptomatic patients or between acute porphyria crises largely relies upon the prevention of potentially life-threatening episodes. At-risk individuals should be counseled to avoid medications known to precipitate attacks (Table 1), to avoid excessive alcohol intake, to seek prompt treatment for other intercurrent illnesses, and to maintain proper nutritional status, including the avoidance of crash dieting. Patients should be encouraged to wear a medical alert bracelet allowing for proper management in the event that the patient becomes temporarily incapacitated as a result of an accident or acute crisis. Photosensitivity can be minimized in VP and HCP patients by avoidance of sun exposure, protective clothing, and pharmacotherapy in the form of a beta-carotene analog, canthaxanthine. Testing for Porphyria By following our suggested testing strategy, the quality of patient care and cost-effectiveness of testing can be maximized. Depending upon the specific type of porphyria suspected, certain tests are more informative than other assays. In general, a 24-hour urine porphyrins (#8562 Porphyrins, Quantitative, Urine) analysis that includes porphobilinogen is the most effective screening tool. However, when EPP is the potential diagnosis, an erythrocyte porphyrin (#8536 Porphyrins, Total, Erythrocytes and #8735 Porphyrins, Fractionation, Erythrocytes) and protoporphyrin fractionation (#8739 Protoporphyrins, Fractionation, Erythrocytes) are the most appropriate tests to perform. For a listing of informative biochemical findings for each type of porphyria, please refer to Table 2. Testing strategies for each suspected porphyria are outlined in Table 3, page 10. Ordering a battery of tests does not enhance the quality of patient care. Rather, a stepwise diagnostic approach is the most effective means of ruling in/out a specific porphyria. In most cases, when the result of the urine porphyrins test is normal, subsequent testing in the form of fecal, plasma, and erythrocyte porphyrin analyses and enzyme assay are not recommended. As shown, the 24-hour urine porphyrins (#8562 Porphyrins, Quantitative, Urine) analysis is the most appropriate starting point. If a 8 11/02

9 Table 2. Informative Biochemical Findings in Porphyria particular diagnosis is suspected, additional first-line testing may be appropriate (tests listed in black in Table 3, page 10); other analyses (listed in red) may be delayed until initial results are available. While providing minimal clinical value, additional testing creates unnecessary expense to the referring laboratory or physician, health insurance company, and patient. For at least 1 week prior to testing for porphyria, and under the guidance of the physician, the use of medications should be avoided or minimized. If clinically inadvisable, or if the patient is in a crisis, a list of medications should accompany the specimen. Additionally, the patient should abstain from alcohol consumption for at least 24 hours prior to specimen collection. Abnormal results are reported with a detailed interpretation including an overview of the results and their significance, a correlation to available clinical information provided with the specimen, differential diagnosis, and recommendations for additional testing when indicated and available. For consultation regarding porphyrias, please contact a laboratory director or genetic counselor in the Biochemical Genetics Laboratory by calling Mayo Lab Inquiry ( ). Continues on page 10. References 1. De Siervi A, Rossetti MV, Parera VE, Mendez M, Varela LS, del C Batlle AM. Acute intermittent porphyria: biochemical and clinical analysis in the Argentinean population. Clin Chim Acta 1999 Oct;288(1-2): Andersson C, Floderus Y, Wikberg A, Lithner F. The W198X and R173W mutations in the porphobilinogen deaminase gene in acute intermittent porphyria have higher clinical penetrance than R167W. A population-based study. Scand J Clin Lab Invest 2000 Nov;60(7): Anderson KE, Sassa S, Bishop DF, Desnick RJ: Disorders of Heme Biosynthesis: X-Linked Sideroblastic Anemia and the Porphyrias (Chapter 124). In The Metabolic & Molecular Bases Of Inherited Disease, 8th edition. Edited by CR Scriver. New York, McGraw-Hill, 2001, pp Matter, SET and Tefferi, A. Acute Porphyria: The Cost of Suspicion. Am J Med 1999 Dec;107: /02 9

10 Continued from page 9. Trichophyton Test Title Change The test name for #82720 Trichophyton Mentagrophytes, IgE has been changed to #82720 Trichophyton Rubrum, IgE to more accurately reflect the test being performed. This is a name change only. Cobalt Serum Specimen Correction In the October 2002 issue the new test announcement for #80084 Cobalt, Serum contained a typographical error in the specimen requirements. The correct specimen volume is 1.0 ml of serum in a Mayo metal-free, screw-capped, polypropylene vial. Table 3. Appropriateness of Testing for Porphyrias Abstracts of Interest Application of Rapid-Cycle Real-Time Polymerase Chain Reaction for the Detection of Microbial Pathogens: The Mayo-Roche Rapid Anthrax Test James R. Uhl, MS; Constance A. Bell, PhD; Lynne M. Sloan, MT(ASCP); Mark J. Espy, MS; Thomas F. Smith, PhD; Jon E. Rosenblatt, MD; And Franklin R. Cockerill III, MD Rapid-cycle real-time polymerase chain reaction has immediate and important implications for diagnostic testing in the clinical microbiology laboratory. In our experience this novel testing method has outstanding performance characteristics. The sensitivities for detecting microorganisms frequently exceed standard culture-based assays, and the time required to complete the assays is considerably shorter than that required for culture-based assays. We describe the principle of real-time polymerase chain reaction and present clinical applications, including the detection of Bacillus anthracis, the causative agent of anthrax. This latter test is commercially available as the result of a collaborative venture between Mayo Clinic and Roche Applied Science, hence the designation The Mayo-Roche Rapid Anthrax Test. Mayo Clinic Proceedings 2002;77: /02

11 Metanephrine/Normetanephrine Test Adds Hypertensive Reference Range Hypertensives <900 µg/24 hour Recently, Mayo added hypertensive reference ranges for Females: Normotensives normetanephrine and metanephrine fractionations. 0-2 years: Not established 3-8 years: µg/24 hour #83006 Metanephrines, Fractionated, 24-Hour, Urine is 9-12 years: µg/24 hour useful as a first- and second-order screening test for the years: µg/24 hour presumptive diagnosis of catecholamine-secreting years: µg/24 hour pheochromocytomas and paragangliomas. Pheochromocytoma is a rare, though potentially lethal, tumor of years: µg/24 hour years: µg/24 hour chromaffin cells of the adrenal medulla that may produce years: µg/24 hour episodes of hypertension with palpitations, severe years: µg/24 hour headaches, and sweating. Patients with pheochromocytoma >70 years: µg/24 hour also may be asymptomatic or present with sustained, rather than episodic, hypertension or an incidentally discovered adrenal mass. Overall, most Hypertensives <900 µg/24 hour TOTAL METANEPHRINE patients who are evaluated for pheochromocytoma will have some history of hypertension. Since hypertensive Males: Normotensives 0-2 years: Not established patients commonly have urine metanephrine/ 3-8 years: µg/24 hour 9-12 years: µg/24 hour normetanephrine levels above the nonhypertensive years: µg/24 hour reference values, application of the nonhypertensive years: µg/24 hour normal values for diagnosis results in unacceptably years: µg/24 hour high false-positive rates of diagnosis. Therefore, years: µg/24 hour including a reference value for hypertensive patients years: µg/24 hour significantly improves our ability to distinguish years: µg/24 hour between non-pheochromocytoma hypertensive patients >70 years: µg/24 hour and pheochromocytoma patients. Hypertensives <1300 µg/24 hour New Reference Values (with Changes Highlighted in Blue) METANEPHRINE Females: Normotensives 0-2 years: Not established Males: Normotensives 0-2 years: Not established 3-8 years: µg/24 hour 9-12 years: µg/24 hour years: µg/24 hour >18 years: µg/24 hour Hypertensives <400 µg/24 hour 3-8 years: µg/24 hour 9-12 years: µg/24 hour years: µg/24 hour years: µg/24 hour years: µg/24 hour years: µg/24 hour years: µg/24 hour years: µg/24 hour Females: Normotensives >70 years: µg/24 hour 0-2 years: Not established Hypertensives 3-8 years: µg/24 hour <1300 µg/24 hour 9-12 years: µg/24 hour years: µg/24 hour Xanthine, Hypoxanthine, Purine, and Pyrimidine >18 years: µg/24 hour Move to LC-MS/MS Hypertensives Recently, the Biochemical Genetics Laboratory <400 µg/24 hour converted #80313 Xanthine and Hypoxanthine, Urine NORMETANEPHRINE Males: Normotensives and #81420 Purine and Pyrimidine Panel, Urine from a 0-2 years: Not established high-pressure liquid chromatography (HPLC)-based 3-8 years: µg/24 hour assay to a liquid chromatography-tandem mass 9-12 years: µg/24 hour spectrometry (LC-MS/MS) method. With this method years: µg/24 hour years: µg/24 hour conversion, there also is a change in the suggested CPT code years: µg/24 hour New CPT Code years: µg/24 hour years: µg/24 hour years: µg/24 hour Previous CPT Code >70 years: µg/24 hour /02 11

12 Meeting Calendar Interactive Satellite Programs... October 22, 2002 Bone Marker Assays: Are They Useful for the Diagnosis & Treatment of Osteoporosis? Presenter: Lorraine Fitzpatrick, MD Moderator: Robert Kisabeth, MD November 19, 2002 HIV Update Presenter: Zelalem Temesgen, MD Moderator: Robert Kisabeth, MD December 10, 2002 Stroke Prevention and Management Presenter: David Wiebers, MD Moderator: Robert Kisabeth, MD For a complete listing of all the courses offered throughout the year, contact the Mayo Reference Services Education Office at or Did You Know? Childhood porphyrias are an uncommon group of metabolic disorders that result from inherited deficiencies of enzymes involved in the heme biosynthetic pathway. Although childhood porphyrias have been reported globally, their exact incidence is unknown. The inheritance patterns of these disorders are complex. Phenotypic variability is common among individual disease states and results partly from the presence of genetic heterogeneity. Childhood porphyrias typically present with photosensitivity and unique skin lesions. Therapy is limited and consists mostly of symptomatic and preventive measures. Although the disease course is variable, mortality from these disorders is rare. For the complete article, see Childhood Porphyrias by Iftikhar Ahmed MD, Mayo Clinic Proceedings 2002;77: The complete article also is available on-line at Communiqué Editorial Board: Lee Aase Kathy Bates Jane C. Dale, MD Tammy Fletcher Terry Jopke Denise Masoner Anita Workman Communiqué Staff: Managing Editor: Denise Masoner Medical Editor: Jane C. Dale, MD Contributors: Iftikhar Ahmed MD; Franklin Cockerill III MD; Patricia Krause; Kara Mensink MS; April Studinski MS, CGC The Communiqué is published by Mayo Reference Services to provide laboratorians with information on new diagnostic tests, changes in procedures or normal values, and continuing medical education programs and workshops. A complimentary subscription of the Communiqué is provided to Mayo Medical Laboratories clients. Stabile Building 150 Third Street SW Rochester, Minnesota MC2831/R , Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. MAYO, Mayo Reference Services and the triple-shield Mayo logo are trademarks and/or service marks of MFMER.

13 Q: A: Ask ( US Why do you contact the ordering physician each time the coproporphyrin isomers test (#8652 Coproporphyrin Isomers, Series I & III, Urine) is ordered? The test for coproporphyrin isomers (#8652 Coproporphyrin Isomers, Series I & III, Urine) is often ordered incorrectly. This assay is primarily utilized to rule in/out the hyperbilirubinemia disorders, Dubin-Johnson or Rotor syndromes. It is not useful in the diagnosis of porphyrias. Bilirubin is derived exclusively from heme metabolism. In Dubin-Johnson and Rotor syndromes, conjugated bilirubin accumulates and transport is suppressed. Hyperbilirubinemia is the key feature of both syndromes. Patients with either disorder have normal liver function tests and histologically normal livers with the exception of gross pigmentation of the liver associated with Dubin-Johnson syndrome. When the coproporphyrin isomers (#8652) test is ordered, referring physicians are contacted via telephone to confirm the diagnosis in question as a means of ensuring the appropriate assay has been ordered. In most cases, the physician is concerned about a potential porphyria diagnosis, and the 24-hour urine porphyrins test (#8562 Porphyrins, Quantitative, Urine) is the appropriate test to order. The specimen requirements are identical, allowing for the coproporphyrin isomers to be canceled and the 24-hour urine porphyrins assay to be ordered. This thereby reduces expenses billed in turn to the referring laboratory or physician, health insurance company, and patient. As a referring laboratory, you can aid in minimizing the turnaround time and telephone calls to you and your referring physicians offices by confirming the suspected diagnosis prior to ordering testing or by providing clinical information with the specimen. If you have questions regarding this, please contact a genetic counselor in the Biochemical Genetics Laboratory by calling Mayo Laboratory Inquiry at Q: A: What is the most appropriate MML test to order when I want an analysis of uroporphyrins and coproporphyrins? In most instances, testing for uroporphyrin and coproporphyrin is requested to rule out porphyria. Urine porphyrin analysis (#8562 Porphyrins, Quantitative, Urine) provides quantitation of uroporphyrins, coproporphyrins, the intermediate porphyrins (pentacarboxyl, hexacarboxyl, and heptacarboxyl), and porphobilinogen. This test is generally the first step in evaluating a patient for porphyria. The interpretive result provided will guide the clinician in selecting additional testing as necessary. The analysis of coproporphyrin isomers (#8652 Coproporphyrin Isomers, Series I & III, Urine) is not a useful diagnostic tool for the porphyrias. This test should not be utilized when testing of uroporphyrins and coproporphyrins are desired. Continued on back 11/02 Ask Us

14 Continued Q: A: If I suspect porphyria, what test should I order? When a porphyria diagnosis is suspected, it is most useful to begin the patient s workup with a single test, the 24-hour quantitative urine porphyrin analysis (#8562 Porphyrins, Quantitative, Urine). Frequently, multiple porphyrin tests are inappropriately ordered on a patient. However, there is no need to begin an evaluation with this extensive level of testing. By beginning the assessment with testing for urine porphyrins and performing further testing only when indicated based upon these results, most porphyrias (see Q/A regarding EPP below), can be ruled out at minimal cost and inconvenience to the patient. When the urine porphyrin analysis yields abnormal results, the interpretive result provided will guide the clinician in selecting any appropriate additional tests. In cases where the results of the urine porphyrin analysis are normal, and the specimen was collected while the patient was experiencing symptoms (such as blistering or an acute crisis), further testing is generally not warranted. However, if the specimen was collected during an asymptomatic period, repeat testing should be considered when the patient is experiencing symptoms thought to be consistent with a porphyria. Q: A: What testing should be ordered when a diagnosis of erythropoietic protoporphyria is suspected? When erythropoietic protoporphyria (EPP) is suspected, the appropriate tests of choice are total porphyrins and protoporphyrin fractionation (#8536 Porphyrins, Total, Erythrocytes or #8739 Protoporphyrins, Fractionation, Erythrocytes) in erythrocytes. Unlike the evaluation of other porphyrias, analysis of urine porphyrins is not useful for this disorder because protoporphyrin is not soluble in urine and other heme pathway intermediates do not accumulate in the urine. Ask Us