Treatment of Inherited Metabolic Diseases

1. Treatment of Inherited Metabolic Diseases Robin Casey, MD Pediatric Resident Teaching 12 May 2011

3. Overview of Inherited Metabolic Disease • over 700 separate IEM described • most present early: in utero 8 % birth - 1 yr 55 % 1 yr-puberty 32 % adulthood 5 % • for many, early detection prior to irreversible pathology may permit intervention with diet or medical therapy to prevent long-term death or disability • approaches to early detection: • symptomatic presentation • screening • IEM affect about about 1/1000 to 1/2000 persons

5. Untreated Phenylketonuria Signs / Symptoms • mental retardation • hypopigmentation • eczema-like rash • autistic-like behavior • autosomal recessive • high blood phenylalanine levels

6. Metabolism of Phenylalanine Dietary Protein Body Protein PHE BH4 (PAH) PPA qBH2 6-pyruvoyl-BH4 Tyrosine PAA PLA GTP Phenylactetyl- glutamine

7. PHE levels in the Newborn with PKU PHE Screening Possible NORMAL RANGE 1 2 3 4 Days of Age

8. Screening screen all babies for increased phenylalanine in blood Microbiological Inhibition assay (“Guthrie test) newer techniques ie Tandom Mass Spectrometry Treatment phenylalanine restricted diet must meet all nutritional needs not just restrict PHE use medical food (restricted in PHE) + normal low protein content foods to provide the tolerated amount of PHE Treatment of PKU Prevents Mental Retardation

11. System for Newborn Screening • all newborn infants are reached • mechanisms exist for determine effectiveness of screening under field conditions: (false + rate / false - rate /threshold levels) • samples analyzed reliably and promptly and results reported promptly • Resources for adequate follow-up (diagnosis & treatment) • Physician & parent knowledge of screening program • Positive cost / benefit ratio if possible

12. Approaches to Treatment • Restriction / supplements / medications • PKU& other aminoacidopathies • Urea cycle disorders • Organic acidopathies (MMA,PA, IVA etc.) • Ensure nutrient availability • Glycogen storage disorders • B-oxidation disorders • Enhancement of organelle function • mitochondrial disorders • Cell / organ replacement • lysosomal storage disorders • Fabry disease & cystinosis

13. Nutritional Treatment of PKU • Diet has two components: • Must meet all nutritional needs + limit intake of restricted nutrients to amts sufficient for growth Medical Formula Contains all nutrientsexcept those being restricted Natural Foods Contains some normal nutrients and all those being restricted +

14. Diet Therapy of PKU PHE level Low PHE Formula Natural food with PHE Total Nutrient Intake Time On Diet

15. Disorders of Branched Chain Amino Acid Metabolism: Isovaleric Acidemia Isovaleryl-CoA Dehydrogenase Deficiency Treat by controlling intake of leucine to meet essential needs for growth and to provide all other nutrients in adequate amounts

16. Case 1: Positive Newborn Metabolic Screen History: • NMS test result shows elevated Phenylalanine (0.75 umole/l; normal <0.125) • Term pregnancy • Normal P/L/D • BWt 3.1 kg, • Normal neonatal course Questions: • Describe briefly what your initial counselling to parents would be. • What investigations would you under take to confirm diagnosis?

17. Results Plasma PHE=1.2umole/l; tyrosine = 0.05 umole/l Urine organic acids increased PPA,PLA,PAA Questions What other tests need to be done to be sure this baby needs diet treatment? 2. What is the basis of the diet treatment? Results of investigations

18. PKU: Diagnostic work-up • Confirm that PHE level is elevated • Rule out biopterin deficiency disorders • Urine pterin levels • Dihydrobiopterin reductase activity • Biopterin load test (optional) • If present start DOPA/carbiDOPA/5HTP • If BH4 disorder not diagnsosed & PHE above 0.4 mM/l, start low PHE diet

19. Nutritional Treatment of PKU • Diet has two components: • Must meet all nutritional needs + limit intake of restricted nutrients to amts sufficient for growth Medical Formula Contains all nutrients except those being restricted Natural Foods Contains some normal nutrients and all those being restricted +

20. Three Children with Maternal PKU Syndrome Mother has untreated PKU during pregnancy(ies) Children are usually not PKU syndrome IUGR post natal FTT Microcephaly Developmental delay Cardiac malformations

21. 5 d.o. male Well for 72 hrs then became lethargic, fed poorly, began vomiting & developed alternating flaccidity & opisthotonic posturing. Became comatose Developed hyperpnea and respiratoy alkalosis progressing to respiratory failure O/E: hepatomegaly, hypothermia What tests would you do? Case 2: Acute Neonatal Presentation

22. 5 d.o. male Well for 72 hrs then became lethargic, fed poorly, began vomiting & developed alternating flaccidity & opisthotonic posturing. Became comatose Developed hyperpnea and respiratoy alkalosis progressing to respiratory failure O/E: hepatomegaly, hypothermia Test Results Normal: CBC, ‘lytes’, bld glucose, lactic acid, urinalysis Low: urea, arginine, ornithine, High: NH3 (350 uM/l), citrulline (1.21 mM/l), glutamine, asparagine ? Diagnosis Case 2: Acute Neonatal Presentation

23. Detoxification of NH3 by Urea Cycle Benzoate Dietary Protein Gut Bacteria Endogenous Protein CatabBuphenyl NH4 PAA NH4 + CO2 GLN Carbamoyl Phosphate GluAPhAcGluNH2 HippuricAcid OrnithineCitrulline Aspartate Urea Arginine Argininosuccinic Acid Fumarate Arginine (CPS) (OTC) (Arginase) (ASAS) (ASAL)

24. Acute Mgmt (based on NH3 level) NPO Dialysis ( prefer. Hemodialysis) IV: CHO (6–8 mg Glc/kg/min) Lipid (3 gm / kg) Alternate Pathway Therapy Oral (Phenylbutyrate + AA) IV (Phenylacetate + benzoate + L-arginine Chronic Mgmt Low protein diet –1.0 to 1.5 gm/kg/d -Cyclinex (ess. AA’s) (up to 50 % of prot) Phenylbutyrate (Buphenyl) (450-650mg/kg/d) Arg / ornith / citrulline Regular monitoring Liver Transplantation Approaches to Therapy of Urea Cycle Disorders

25. Organ Transplantation(to provide metabolic capability) Liver • Urea Cycle disorder • Familial Hypercholesterolemia (LDL-cholesterol receptor deficiency) • Tyrosinemia • Glycogen Storage Disease (Type I) • Primary hyperoxaluria * Kidney • Fabry Disease • Cystinosis • Primary hyperoxaluria * Bone Marrow • Various lysosomal storage diseases ie. Hurler syndrome (MPSI) Cornea • Cystinosis, Fabry disease

26. Liver Transplantation • For disorders where liver is the primary organ involved • “cure” means the transplant prevents the disease process • 4% of pediatric liver failure is of metabolic origin

27. Liver transplantation and UCD’s • Corrects protein tolerance… can enjoy normal diet • Eliminates hyperammonemic crises • Needs to be performed as early as possible to prevent irreversible brain damage • Other organ involvement ie. CNS

28. Maintainence of Euglycemia during Fed & Fasting States Maintenance of blood and tissue glucose levels is critical for function • CNS function (except in the infant, CNS is almost completely dependent on glucose from the blood for energy • other tissues also require glucose but can utilize other energy sources as well ie fatty acids and amino acids, glycerol and lactate

29. Requirements to Maintain Euglycemia Under “Fasting” Conditions • Functioning hepatic gluconeogenic & glycogenolytic enzyme systems • adequate endogenous gluconeogenic substrates (amino acids, glycerol, lactate) • adequate B-oxidation of fatty acids to synthesize glucose & ketones • functional endocrine system to modulate & integrate the above system components

30. Phases of Glucose Homeostasis 1.Glucose absorptive phase: 3 - 4 hrs after glucose ingestion (high insulin) 2.Post absorptive/early starvation: 3-12 hrs glucose (from hepatic glycogen) to brain, RBC, renal medulla 3. Early / Intermediate Starvation: 14+ hrs gluconeogenesis & (later) lipolysis

31. Case 3: patient & liver biopsy

32. Questions • What types of disorders might cause this appearance? • What further historical information may be of help? • What further studies should you request from the pathologist?

33. Questions • What types of disorders might cause this appearance? • Glycogen storage disorders (types 1a & 1b, 3, 6) • Lysosmal storage disorders (Gaucher, Niemann-Pick, MPS, oligosaccharidoses • B-oxidation disorders (MCAD, LCHAD, VLCAD) • What further historical information may be of help? • Symptoms of hypoglycemia (relationship to fasting including timing) • Mother indicates baby can only go about 2-4 hours without a “bottle” • What further studies should you request from the pathologist? • PAS staining +/- pretreatment with diastase • Electon microscopy

34. GSD-II ( lysosomal) GSD-IV GSD-V,GSD-VI,GSD-IX GSD-0 GSD-III GSD-1a&b GSD-VII GSD-X,GSD-XII,GSD-XIII GSD-XI (LDH) LIVER MUSCLE

35. Diagnostic testing • Fasting challenge +/- feeding challenges • Enzyme assays • Need fresh liver • Need to choose specific enzymes to target based on history • Molecular testing • Now have bank of mutations but expensive

36. Glycogen Storage Disease: Controlled Fast

37. Clinical features early onset hypoglycemia lacticacidosis hepatomegaly Fanconi syndrome hyperuricemia hyperlipidemia Diagnosis controlled fast (test BS & LA) enzyme (liver biopsy) DNA testing Therapy provide 5 - 10 mg glucose/kg/min continuous .nocturnal infusion of CHO as polycose or formula frequent meals during days corn starch days &/or nights don’t over treat with CHO Neutropenia in Type IB prophylactic antibiotics GCSF Emergency protocols for illness, surgery etc. GSD IA &IB

38. Case 4: 18 month boy with hepatomegaly and obtundation History: • The ER physician calls about an 18 month old boy who is admitted in stuporous state following being found pale & sweaty and unarousable by parents • Had been ill for about 18 hours with refusal to eat anything other then a few ice chips • Had a seizure in ambulance on way in Initial studies: • Blood sugar = 0.2 mM/l, Na+=145, K+ =3.5, Cl-=104, TCO2 = 10 • Urinalysis = Normal • All other testing including lactate, NH4 & LFE’s normal WHAT IS YOUR INITIAL ASSESSMENT? HOW SHOULD YOU PROCEED WITH HIS DIAGNOSTIC STUDIES & CARE?

39. Key observations • Severe hypoglycemia with hepatomegaly and no ketonuria on setting of history of prolonged fasting • Needs urgent treatment of hypoglycemia • Route? • How much glucose? • ? Significance of no ketones in urine • ?diagnostic testing

41. VLCAD,MCAD, SCAD Trifunctional protein

42. Diagnostic Investigations • Plasma acylcarnitnes suggest Medium Chain Dehydrogenase deficiency (MCAD) • Plasma free carnitine levels low while acylcarnitines high • 14C- palmitic acid oxidation in leucocutes quite reduced • Molecular diagnosis indicates homozygosity for the common caucasian mutation.

43. MS/MS Analysis of plasma acylcarnitines (?= MCAD)

44. Phases of Glucose Homeostasis 1.Glucose absorptive phase: 3 - 4 hrs after glucose ingestion (high insulin) 2.Post absorptive/early starvation: 3-12 hrs glucose (from hepatic glycogen) to brain, RBC, renal medulla 3. Early / Intermediate Starvation: 14+ hrs gluconeogenesis & (later) lipolysis

45. Treatment: MCAD • Avoid fasting • L-carnitine if free carnitine low • Emergency protocol & letter • Sick day management • Admission to ER/hospital to maintain blood glucose with IV infusion to prevent excessive lipolysis the would overload the B-oxidation pathway

46. Lysosomal Storage Diseases • Characterized by excessive accumulation of undigested large molecules in the lysosome • Caused by: • Lack of a single or a group of lysosomal hydrolase degradative enzymes in lysosme • Inability to transport material out of lysosome into cytoplasm • Due to genetic mutations affecting important proteins including enzymes or transport proteins

47. Salla Disease FibroblastsDistended Lysosomes

48. Oligosaccharide & Glycopeptidoses Mannosidoses, fucosidosis, Schindlers, sialidoses, aspartylglycosaminuria Multiple Enzyme Deficiencies I-cell & MLIII, multiple sulfatase deficiency, galactosialidosis Transport Deficiencies Cystinosis, Salla disease, ISS Peptidoses Pycnodysostosis, infantile NCLF Sphingolipidoses Tay-Sach’s, Sandhoff, GM1 gangliosidosis, MLD,Krabbes, Fabry, Gaucher, Farber, Niemann-Pick Mucopolysaccharidoses Hurler/ Hurler-Scheie/Scheie,Hunter, San Filippo, Morquio, Maroteau-Lamy, Sly Glycogenoses Pompe Lipid Storage Diseases Wolman, cholesterol ester, NP”C” 40+ Lysosomal Storage Diseases Identified

49. Alleviation of symptoms / palliative care Drugs: Cystagon in cystinosis Bone marrow transplant’n –MPS-I Enzyme replacement therapy Biosynthesis inhibitors Chaparone Therapy Gene therapy LSD’s: Treatment Approaches

50. Cystinosis • Inability to transport cysteine out of lysosome • short stature,renal failure, corneal clouding, hypothyroidism, mild dementia (late-onset) • Treatments: • renal transplant • Cystagon & phosphocysteamine