Metabolic Muscle Disease

Transcription

1 Metabolic Muscle Disease Dr. Simon Olpin Consultant Clinical Scientist in Inherited Metabolic Disease Department of Clinical Chemistry Sheffield Children s Hospital

2 Clinical Diagnosis of Muscle Disease A multi-disciplinary approach Physiology / Electrophysiology Magnetic Resonance Imaging & Spectroscopy Histopathology (histology & immunocytochemistry) Biochemistry Genetics Haematology

3 Causes of Muscle disease Structural/linkage proteins Contractile proteins Ion Channel proteins Inflammatory & autoimmune myopathies Endocrine disorders Toxic myopathy e.g. statins Defects of muscle energy metabolism

4 Causes of myoglobinuria Tein I (1996) Seminars in Ped Nur 3(2) 59 Age range years Age range - Childhood diagnosis in 47% (77) CPT GSD V McArdle s 10 2 Phosphorylase b kinase 4 0 Phosphoglycerate kinase 1 1 Myoadenylate deaminase (AMP) 3 0 Phosphoglycerate mutase 0 3 Lactate dehydrogenase 0 1 AMP + CPT diagnosis in 23% (100) NB. Absence of VLCAD Respiratory chain

5 Clinical presentations of defects of FAOD Hypotonia /delayed development Exercise intolerance/chronic weakness/muscle pain/stiffness/cramps/atrophy/contractures Acute rhabdomyolysis / renal failure Respiratory / neck muscle involvement, wheelchair dependency / episodic ketoacidosis Ponto bulbar palsy, deafness Peripheral neuropathy / polyneuropathy / abnormal gait

6 Synergistic heterozygosity Combined defects myoadenylate deaminase deficiency Found in ~ 2% of muscle biopsies PLUS partial deficiency/carrier status for another defect e.g. partial CPTII deficiency plus myoadenylate deaminase deficiency OR carrier status for two other separate disorders Vladutiu G (2001) Mol Genet Metab 74:51-63 Vockley et al (2000) Mol Genet Metab 71:10-18

7 Presentation with pain / stiffness / weakness / rhabdomyolysis / bulbar palsy Family History of Disease Exclude non-metabolic causes: -inflammatory myopathies -toxicological, infection Full Clinical Examination Neurological, Gastrointestinal / liver, Cardiac, Opthalmology, Audiology 1 st line Biochemical Investigations Plasma Urine Lactate Organic acids Creatine kinase Acylcarnitines Free carnitine Consider Additional Testing (non invasive) Forearm exercise testing Exercise testing (e.g. treadmill studies) Nerve conduction studies P-MRS, EMG

8 Fatty Acid Oxidation defects can cause mild/moderate neuro / myopathic disease Exercise intolerance - pain /stiffness/myoglobinuria typically on prolonged sustained exercise exacerbated by poor food intake / cold / heat There may be myalgia with intercurrent infection Peripheral polyneuropathy & episodic rhabdomyolysis mild TFP deficiency / (?)LCHAD Progressive myopathy/acute encephalopathy rr-madd CK usually normal between episodes Urine organic acids sometimes abnormal DCA & (OH)DCA Acylglycines Plasma acylcarnitines MAY be abnormal

9 Detection of FAOD s Preliminary investigations Urine OA s Plasma free carnitine /acylcarnitine profile CK NB. It is important to send samples to a recognised metabolic centre as many of the biochemical abnormalities are subtle! 06/05/11

10 Detection of FAOD s Second line investigations skin biopsy for fatty acid oxidation studies specific enzyme assay on fibroblasts e.g. CPTII mutation studies Generally NOT MUSCLE BIOPSY CPT & VLCAD assays in muscle not usually reliable

11 What do we offer at Sheffield Children s Hospital? A Fatty Acid Oxidation Service UK and beyond e.g. Dublin & Toronto Children s Hospitals Investigate >400 patient fibroblast cell lines each year measure the rate of fatty acid oxidation ( using 3 fatty acids) The results tell us if there is a defect that slows the rate of fatty acid oxidation in the patient fibroblast acylcarnitine profiling Pattern of abnormal by-products of fatty acid oxidation Helps to pinpoint what step in fatty acid oxidation is affected Individual enzyme assays e.g. CPT I, CPT II, CAT, LCHAD, carnitine transporter activity Molecular Genetics full mutation CPTII, CAT, GSDV & the rest

12 Fatty acid oxidation CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 COOH Sources of long chain fatty acids for use as fuel during fasting /sustained exercise Diet Adipose tissue Long chain fatty acids are oxidised in the body to produce carbon dioxide (CO 2 ), water (H 2 O) & energy (ATP)

13 How we measure fatty acid oxidation MUSCLE CELLS fatty acid oxidation enzymes (+ Kreb s cycle + RES) Fatty acid CO 2 + H 2 O + energy OUR ASSAY in fibroblasts fatty acid oxidation enzymes Labelled fatty acid 3 H CO H 2 O + energy

14 3 H release from labelled [9,10-3 H] fatty acids [9,10-3 H]Myristic acid (C14:0) CH 3 CH 2 CH 2 CH 2 C 3 H 2 C 3 H 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 COOH [9,10-3 H]Palmitic acid (C16:0) CH 3 CH 2 (CH 2 ) 3 CH 2 C 3 H 2 C 3 H 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 COOH [9,10-3 H]Oleic acid (C18:1) CH 3 (CH 2 ) 5 CH 2 CH 2 C 3 H C 3 H CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 COOH

15 % Oleate Detection of VLCAD using [9,10-3 H]substrates in fibroblasts CONTROLS mild VLCAD 40 severe VLCAD 20 LCHAD Ratio Palmitate/Myristate

16 Diagnosis FAOD that can cause muscle disease (Sheffield) All fatty acid oxidation defects ~ 400 Myopathic CPTII 31 Myopathic CPTII carrier only 5 Myopathic VLCAD 16 rr-madd (myopathic) 20 Brown-Vialetto Van Laere 3 Mild TFP 3 Primary Carnitine Deficiency 35 SCAD (?) 9

17 Carnitine Palmitoyl Transferase type II Deficiency Three phenotypes of CPTII deficiency neonatal / infantile with/without cardiomyopathy Late onset (mild) - myopathic with rhabdomyolysis Prolonged exercise related exacerbated by heat/cold/stress/poor food intake MYOPATHIC - most common inherited cause of myoglobinuria in young adults

18 Diagnosis of mild CPTII Clinical suspicion myalgia in young children rhabdomyolysis in adolescence / adults All biochemical parameters may be normal between episodes but:- raised plasma C 18:1 + C 16 /C 2 ratio Muscle biopsy may be abnormal (~20% lipid) muscle CPTII assays are usually unreliable!! Fibroblasts fatty acid o C acylcarnitine profiling C 16, C 18 Specific CPT II assay in fibroblasts (will detect carriers!!) Mutation analysis Common S113L mutation (accounts for ~50% of disease)

19 Very long chain acyl-coa dehydrogenase deficiency (VLCAD) Three phenotypes neonatal / infantile with/without cardiomyopathy mild - late onset MILD (onset usually >10 years) exercise intolerance (prolonged) rhabdomyolysis may be exacerbated by missing meals / cold / heat raised C14:1 acylcarnitine in plasma NOT ALWAYS!!

20 The Biochemical defect in MADD Ketone bodies Acetyl-CoA TCA S EFAD EFADH 2 ETFox SH 2 Very-long-chain acyl-coa DH Medium-chain acyl-coa DH Short-chain acyl-coa DH Long-chain acyl-coa DH Acyl-CoA DH-9 Short/branched-chain acyl-coa DH Isobutyryl-CoA DH Isovaleryl-CoA DH Glutaryl-CoA DH Dimethylglycine DH Sarcosine DH ADP ETFred H+ H+ H+ Fatty acid metabolism Amino acid metabolism Choline metabolism ATP ETFQO I II Q III Cytc IV V H+ Background

21 The defect in riboflavin-responsive MADD? TCA EFAD EFADH 2 ETFox Very-long-chain acyl-coa DH Medium-chain acyl-coa DH Short-chain acyl-coa DH Long-chain acyl-coa Acyl-CoA DH-9 Short/branched-chain acyl-coa DH Isobutyryl-CoA DH Isovaleryl-CoA DH Glutaryl-CoA DH Dimethylglycine DH Sarcosine DH ADP ETFred H+ H+ H+ Fatty acid metabolism Amino acid metabolism Choline metabolism ATP I II ETFQO Q III Cytc IV V H+ Background

22 The defect in riboflavin-responsive MADD? Riboflavin FMN FAD TCA EFAD EFADH 2 ETFox Very-long-chain acyl-coa DH Medium-chain acyl-coa DH Short-chain acyl-coa DH Long-chain acyl-coa DH Acyl-CoA DH-9 Short/branched-chain acyl-coa DH Isobutyryl-CoA DH Isovaleryl-CoA DH Glutaryl-CoA DH Dimethylglycine DH Sarcosine DH ADP ETFred H+ H+ H+ Fatty acid metabolism Amino acid metabolism Choline metabolism ATP ETFQO I II Q III Cytc IV V H+ Background

23 How should these ETFDH mutations give rise to a riboflavin-responsive phenotype? For several flavoproteins, FAD-binding has been demonstrated to promote assembly and/or stabilization of holoenzyme Nagao and Tanaka 1992; Saijo and Tanaka 1995; Sato et al., 1996 Hypothesis We hypothesise that the ETFDH mutations cause impaired FADbinding /-stabilization thereby increasing intra-cellular degradation of mutant ETFQO protein. The vulnerability to degradation could be modulated by the FAD content of the cell resulting in a riboflavin-responsive phenotype

24 Poor riboflavin status a disease triggering factor? Symptoms may have been precipitated by a deterioration in riboflavin status during adolescence. The national Diet and Nutrition Survey of young people aged 4-18 y has reported a high prevalence (95%) of poor riboflavin status among adolescent girls in the UK Gregory Interestingly, 12 of our 16 patients are adolescent girls.

25 Brown-Vialetto-Van Laere Syndrome BVVL or Fazio Londe syndrome FL BVVL Sensorineural deafness plus variety of cranial nerve palsies FL same disease without the deafness Usually presents in second decade of life (progessive ponto-bulbar palsy) Limb weakness Difficulty breathing Slurred speech & difficulty swallowing Facial weakness Neck & shoulder weakness May include mental retardation & seizures 30% patients survive >10 years after diagnosis

26 Brown-Vialetto-Van Laere Syndrome RFT2 riboflavin transporter 2 (rats) riboflavin transporter small intestine mutations in C20orf54 gene Bosch et al J Inher Metab Dis 34(1), Brown-Vialetto-Van Laere and Fazio Londe syndrome is associated with a riboflavin transporter defect mimicking mild MADD: a new inborn error of metabolism with potential treatment.

27 Brown-Vialetto-Van Laere Syndrome BVVL or Fazio Londe syndrome FL OR presents in infants often without deafness Neurological deterioration Hypotonia Respiratory insufficiency Early death

28 Diagnostic clues Urine organic acids Often subtle but variable metabolites as seen in MADD i.e. isobutyrylglycine, isovalerylglycine, hexanoylglycine, suberylglycine, ethylmalonate, 2-hydroxyglutarate

29 Diagnostic clues Plasma acylcarnitines Often subtle but variable metabolites as seen in MADD i.e. generally mild increases in C4-C12 acylcarnitines Low plasma FAD, FMN or EGRAC

30 Treatment Usually responds well to riboflavin 100 mg /day in two doses Early treatment to prevent irreversible paralysis of diaphragm

31 Muscle disease Could this be metabolic? CK Urine organic acids Plasma acylcarnitines Fibroblasts/ (?)mutation analysis Riboflavin responsive disorders are under diagnosed!

32 Acknowledgements Shirley Clark Helen Hind Camilla Scott Nigel Manning Melanie Downing Rodney Pollitt Mark Sharrard Jim Bonham Joanne Croft Jane Dalley Rikke Olsen