Hyperammoniemia: Part 1:diagnostic clues and investigations. Hyperammoniemia. Differential diagnosis: non metabolic hyperammoniemias.

Transcription

1 Hyperammoniemia: Part 1:diagnostic clues and investigations Vassili Valayannopoulos,, M.D. Reference Center for Inherited Metabolic Disorders NeckerEnfants Malades,, Paris, France Hyperammoniemia Definition: NH3> 100μmol/l in newborns NH3 > 50μmol/l in children or adults Origin of NH3: Nitrogen protein catabolism proteins aminoacids A zo ingested protein cellular protein alanine from muscle aminoacid αketoglutarate NADH + NH + 4 transaminase portal blood GDH αketoacid glutamate NAD + + H 2 O TCA CYCLE UREA CYCLE perivenous hepatocyte Glutamate+NH 4 + +>glutamine GLUTAMINE SYNTHETASE musclebrainperiportal hepatocyte. AMINOACIDS METABOLISM. R CH COOH NH 2 αamino acid Transamination Glu deamination R C COOH NH 3 O αceto (oxo) acid Ammonia BOxidation Urea Cycle CO 2 + H 2 O + UREA Fatty acids Gln AcylCoA Pyr PDH PC βox (+) Glnase Glu AcCoA NAGS () OA Glu () PrCoA NAG 2KG Asp NH 3 (+) () HCO 3 CP CPSI 2 H + Mitochondrion Cytosol CP Orotic acid UREA UREA CYCLE ARG Glu Arg Asp ASS AMP + PP ASL Fumaric ASA Differential diagnosis: non metabolic hyperammoniemias Any disease where liver circulation or function is impaired Portosystemic shunts (ultrasound( ultrasound+++) Acute liver failure Transient hypernh3 of the newborn Valproate therapy Infection with urease + bacteria Chemotherapy (asparaginase)

2 Hyperammoniemia and IEM 1. Accumulation of toxic substrates due to an enzymatic bloc INTOXICATION Urea Cycle Disorders, Aminoacidopathies, organic acidurias Sugar intolerance: Galactosemia, fructose. 2. Impairment of energy production due to lack of energy fuel (glucose, ketone bodies, fatty acids ) or by processing impairment ENERGETIC DEFICIENCIES Glycogenolysis, gluconeogenesis, glycolysis defects Fatty acid oxidation defects Respiratory chain disorders, Krebs cycle disorders 3. COMPLEX MOLECULES PRCOCESSING Lysosomal storage diseases Peroxysomal diseases Congenital Disorders of Glycosylation. Hyperammoniemia in IEMs Urea cycle disorders (enzyme deficiency) Lack of essential substrates: Bicarbonate (acidosis: organic acidurias,, lactic acidosis) Glutamate (primary or secondary Krebs cycle disorders, GDH hyperactivity), branched chained aminoacids (MSUD), acetylcoa (FAO) Energy impairment (FAO, Krebs cycle, respiratory chain disorders) UCDs: : Clinical presentations Acute Coma (neonate, child, adult) Liver failure (any age) Coma + liver failure= Reye syndrome Psychiatric Chronic Vomiting, selflimitation of protein Mental Retardation Epilepsy aggravated by valproic acid (DEPAKINE ) Psychiatric ( with acute attacks) Organic acidurias Leucine Isoleucine B2, FAD 3MéthylcrotonylCoA 3OH3MéthylglutarylCoA 2Méthylacétoacétyl CoA lyase Thiolase transamination B6 Ac.2Oxoisocapro Oxoisocaproïque Ac 2oxo2 oxo3ch3n valérique B1, NAD Isovaléryl rylcoa 2 MéthylbutyrylM thylbutyrylcoa carboxylase B8 3MéthylglutaconylCoA 2Méthyl 3OHbutyryl CoA hydratase Acétoac toacétatetate décarboxylase Acétyl tylcoa Acétyl tylcoa TiglylCoA PropionylCoA Carboxylase MalonylCoA B8 MéthylmalonylCoA Valine Ac 2oxoisoval2 oxoisovalérique Isobutyryl CoA MéthylacrylylCoA 3OHisobutyryl CoA déacylase Ac 3OHisobutyrique 3 Méthylmalonic semialdéhyde racemase + mutase SuccinylCoA B12 cytosol mitochondrium OA: clinical presentations Acute neonatal Free interval, ComaC oma, Küssmaul tachypnea (acidosis), dehydration (MMA++), sweaty feet odor (IVA) Hypertonia, dystonia,, abnormal movements Late Onset Coma (triggered by fasting, infection) Mental retardation Cardiomyopathy (PA) Renal failure (MMA) MSUD: clinical presentation Free interval, neonatal coma Axial hypotonia,, peripheral hypertonia Abnormal movements (boxing, pedalling) Particular body and urine odour ( maple( syrup, curry ) Late onset forms: Mental retardation Acute attacks with coma

3 FAO defects: clinical presentation Brutal coma, convulsions (hypoglycemia( hypoglycemia) Hepatomegaly (liver dysfunction or failure) Cardiomyopathy (SIDS) Heartbeat disorder (SIDS) Muscular hypotonia,, red port wine urine (rhabdomyolysis:myopathic form) Krebs cycle dysfunction = cataplerosis Pyruvate carboxylase deficiency French type (neonatal) Neonatal hypotonia, hypoglycemia Tachypnea (Küssmaul)) (lactic acidosis) American type (late onset) Mental retardation Citrin deficiency Neonatal Hypotonia, icterus, hypoglycemia, hepatomegaly (liver dysfunction or failure) Infant and children: apparently healthy, dislike sugar Late Onset (adult) Coma, liver cirrhosis, hepatocarcinoma Other characteristic clinical presentations GDH hyperactivity (HIHA syndrom) Hypoglycemia (hyperinsulinic) early or lateonset, rarely neonatal Mental Retardation (mild to severe) Epilepsy (absencemyoclonic) Lysinuric protein intolerance failure to thrive, hepatosplenomegaly, hematological disease (hemophagocytosis) respiratory distress (proteinosis) Lys mental retardation (mild) Gly LysGly Other characteristic clinical presentations OAT deficiency: gyrate atrophy of retina, blindness P5C synthase deficiency (2 cases) Cataract, mental retardation, joint laxity!! Fasting hypernh3 ; normal in the fed state Lys LysGly Coma+ Hyper NH3 : simple biochemical hallmarks UREA CYCLE DISORDERS NH3 from hour to hour ph>7.4 (respiratory( alcalosis) Lactate: N, Glucose: N Ketone bodies : or + ORGANIC ACIDURIAS (MMA, PA, IVA) NH3 ph metabolic acidosis+++ Lactate, Ketone bodies +++ MSUD NH3: N or, Lactate, ph: N Ketone bodies: N or +, DNPH:+++ Urine odor: «maple suryp,, curry» FAO defects: hypoglycemia, liver failure, ALT, AST, CK HyperNH3 without coma Krebs cycle dysfunction Pyruvate carboxylase: lactate, KB: Citrin deficiency: liver failure, hypoglycemia, galactosemia, tubulopathy GDH hyperactivity: hyperinsulinismhyperammoniemia syndrome Recurrent hypoglycemia (hyperinsulinism)+++

4 ENZYMES AND TRANSPORTERS INVOLVED IN HYPERNH3 1 Urea cycle disorders: Nacétylglutamate synthase NAGS Carbamylphosphate synthétase I CPSI ithine carbamyltranféraseoct or Argininosuccinate synthétase (citrullinemia type I) Argininosuccinate lyase (argininosuccinic aciduria) Arginase 2 Transporter deficiency: ORNT1 (Triple H) y+l (4F2hc/y+LAT1) (Lysinuric protein intolerance) Citrin (citrullinemia type II) 3 «Satellite» enzyme deficiency: 1pyrroline5carboxylate synthase (P5C synthase) Pyruvate carboxylase ithine Amino Transferase (OAT) 4 Secondary hyper NH3: Organic acidurias (propionylcoa carboxylase, methylmalonyl CoA mutase, isovalerylcoa dehydrogenase) Fatty acid oxidation defects GDH hyperactivity (hyperinsulinismhyperammoniémia) DIAGNOSTIC TOOLS Ammonia mesurement Aminoacid chromatography (plasma and urine) Organic acid chromatography (plasma and urine) Orotic acid (urine) Loading tests Carbamylglutamate test Enzymatic assays Molecular diagnosis AMMONIA MEASUREMENT Fatty acids UREA CYCLE 1. OVERESTIMATION Delay from sampling to analysis Serum Transportation at room T : T Gln Glu + NH 3 ( 600 µm) Contamination by exogenous NH3: Ammonium Heparinate Solvants (chromatography) Cleaning products Cigarette smoke Gln AcylCoA Pyr PDH PC βox (+) Glnase Glu AcCoA NAGS () OA Glu () PrCoA NAG 2KG Asp NH 3 (+) () HCO 3 CP CPSI 2 H + Mitochondrion Cytosol CP Orotic acid UREA ARG Glu Asp ASS AMP + PP ASA ASL Arg Fumaric AA CHROMATOGRAPHY: DIAGNOSTIC ALGORITHM CONGENITAL HYPERAMMONEMIAS Preterm THAN Present Symptoms before 24h of life Full term IEM GAII Others Low or N Present PA,MMA,IVA βox Ds Absent IEM Acidosis +/ ketosis Absent UCDs Plasma citrulline 015 µm µm > 1000 µm Plasma High or N ASA ASA=0 Gln N ou Ala Gly Cit N Organic Aciduria? Ala Gly Cit <20µM µM >500µM 2550µM LATE ONSET HYPERAMMONIEMIAS With Acidosis Without Acidosis ASA ASA=0 Arg Ala Gly N ++ Cit N or HomoCit Ala Gly N ou Cit ± Lys AACu Cit Arg Ala N Pro Cit Normal U Orotate High CPSD D HHH ASLD ASSD NAGSD Modified from S.W.Brusilow and A.L.Horwitch, in The metabolic and molecular bases of inherited diseases, pp , 2001 OACu Orot () Orot (+) CPSD D ASLD ASSD ARGD HHH LPI P5CSD NAGSD

5 RULLINE <20µM >40µM NB<1wk Intestinal RCD UCD Kidney PC UCD disease (NARP) Carbamylphosphate Synthetase II Transcarbamylase OROTIC ACID Glutamine HCO 3 CarbamylP Carbamyl aspartate NH + 4 HCO 3 CPSI CarbamylP ithine Citrulline NAGS HHH P5CS CPSI ASS ASL LPI 2 Dihydroorotase Dehydrogenase Ala Gln Gln Gln Pro Ala Ala Ala N Lys Lys Nou Lys N Arg Arg Arg hcitu ++ Pro AAR ± Cys2 3MeHis Gln Ala ou Lys Gln Gln Ala Ala Lys Lys AAS Gln Ala LysP P ArgP LysU U ArgU Cys2U OROTIDINE Orotate:PRPP Transferase OMP Decarboxylase OROTATE PRPP Orotidine5 phosphate Uridine5 phosphate From S.W.Brusilow and A.L.Horwich in The metabolic and molecular bases of inherited disease; pp ; 1997 LOADING TESTS 1 allopurinol loading orotic acid measurement in urine 2 Protein loading test (acute): 1g protein/ kg in a single meal Carbamylphosphate Synthetase II Transcarbamylase Glutamine HCO 3 CarbamylP NH + 4 HCO 3 CPSI CarbamylP ithine plasma NH 3 orotic acid (urine) Dihydroorotase Carbamyl aspartate Citrulline 3 Protein loading test + allopurinol NH 3 AND orotic acid 2 4 Protein loading test (chronic: 3 or 4 days): 5g protein/kg/d Plasma NH 3 : before and after each meal or if symptomatic (headache, dizziness, altered behavior) NH 3 measurement= EMERGENCY Orotic acid: urine collection every 6 hours during the test Dehydrogenase OROTATE PRPP Orotate:PRPP Transferase Orotidine5 phosphate OROTIDINE OMP () Decarboxylase Uridine5 phosphate From S.W.Brusilow and A.L.Horwich in The metabolic and molecular bases of inherited disease; pp ; 1997 ALLOPURINOL Xanthine Oxidase Oxipurinol Oxipurinol ribonucleotide CARBAMYLGLUTAMATE TEST Distinction between NAGSD and CPSD when the patient has hypernh3 NH 3 decreases in NAGSD Plasma citrulline: will not raise if CPSD will raise if NAGSD Citrulline variations in CPSD depend on residual activity Enzyme Tissue Quantity of tissue required Stability Activity NAGS Liver 30 mg CPSI Liver 10 mg 1.84 ± ASS Liver Intestinal mucosa Liver Fibroblasts 10 mg 10 mg ± ± mg ± ASL Liver 20 mg ± 2.26 ± ARG Liver Erythrocytes ENZYMATIC ASSAYS 10 mg 5 ml sang total ± 435 ± ± J.P.Colombo, Berne, Switzerland 2. D.Rabier, Laboratoire Biochimie B, Hôpital NeckerEnfants Malades, Paris, France

6 MOLECULAR DIAGNOSIS All genes of enzymes of the urea cycle have been identified Various mutations have been reported for all defects no predominant mutations ex: 244 mutations for (Tuchman, 2002) Now, let me hand it over to Carlo. Diagnostic tool NAGS, CPS and citrullinemia type II genotypephenotype correlations (ex. lateonset, female carriers) Prenatal diagnosis+++