DR.GOKULDAS P K Junior resident in PediatricsGovt.medical college, Kozhikkode
Approach to Inborn errors of metabolism in Neonates
Introduction to IEM
Differential diagnosis of any sick neonate
IEM are individually rare
Overall incidence upto 1 in 2000
High index of suspicion for diagnosis
Clinical pointers
Deterioration after a period of apparent normalcy
Parental consanguinity
Family history of neonatal deaths
Rapidly progressive encephalopathy and seizures
of unexplained cause
Severe metabolic acidosis
Clinical pointers
Persistent vomiting
Peculiar odor
Acute fatty liver or HELLP (long-chain-3-
hydroxyacyl-coenzyme dehydrogenase
deficiency (LCHADD).
Clinical presentati ons
Neurologic deteriorationWith metabolic acidosis
• MSUD• organic acidurias• fatty acid oxidation defects• Primary lactic acidemias (defects of
gluconeogenesis, glucogenolysis, pyruvate metabolism, Krebs cycle, and respiratory chain)
Neurologic deterioration
With hypoglycemia
• organic acidurias
• fatty acid oxidation defects
• defect of gluconeogenesis
Neurologic deterioration
With hyperammonemia
• Urea cycle defects
• Propionic acidemia
• Methyl malonyl acidemia
Seizures
Seizures
Non-ketotic hyperglycinemia in uteroPyridoxine –responsive seizures, 1st dayPyridoxal phosphate responsive seizures 1t
dayFolinic-acid responsive seizures 1st daySulfite oxidase/molybdenum co-factor defect Peroxisomal disordersDisorders of creatine biosynthesis & transport
Hypotonia
Mitochondrial respiratory chain defects
Peroxisomal disordersNon-ketotic
hyperglycinemiaSulfite
oxidase/molybdenum co-factor defect
Liver dysfunction
Hepatomegaly with hyoglycemiaGluconeogenesis defects(GSD)
Liver failureGalactosemiaHereditary fructose intolerancetyrosinemia type IFAO defectsMitochondrial respiratory chain defects
Cholestatic jaundice with failure to thrive:
alpha-1-antitrypsin deficiency
Niemann-Pick disease type C
Inborn error of bile
acid metabolism
Peroxisomal disorders
Citrin deficiency
Cardiac dysfunction
Fatty acid oxidation defects
Carnitine uptake deficiency
Carnitine-acyl Carnitine translocase deficiency
Carnitine palmitoyl transferase ll deficiency
LCHAD deficiency
Trifunctional protein deficiency
VLCAD deficiency
Cardiac dysfunction
Glycogen storage diseasesPompe diseasePhoshorylase b kinase deficiency
Mitochondrial electron transport chain defectsTCA cycle defects
Alpha keto glutarate dehydrogenase deficiencyLysosomal storage disorder
I -cell disease
Apnea
Long Chain Fatty acid oxidation defects
Non ketotic hyperglycinemia
Abnormal urine odor
Glutaric acidemia (type II):Sweaty feetIsovaleric acidemia: Sweaty feet
Multiple carboxylase deficiency: Tomcat urine
Maple syrup urine disease: Maple syrup odour of urine
Hypermethioninemia: Boiled cabbage urine odor
Miscellaneous
Lens dislocation : Sulfite oxidase deficiency
Skin changes : Biotinidase deficiency HCS deficiency
Dysmorphic Features
Peroxisomal disorders : Zellweger syndromeLarge fontanelle prominent forehead flat nasal bridge epicanthal folds hypoplastic supraorbital
ridges
Dysmorphic Features
Pyruvate dehydrogenase deficiencyEpicanthal folds flat nasal bridge small nose with
anteverted flared alae nasi
long philtrum
Dysmorphic Features
Glutaric aciduria type IIMacrocephaly high forehead flat nasal bridge short anteverted nose ear anomalies hypospadias rocker-bottom feet
Dysmorphic Features
Cholesterol biosynthetic defects Smith-Lemli-Opitz
syndrome: Epicanthal folds, flat nasal
bridge, toe 2/3 syndactyly, genital abnormalities, cataracts
Dysmorphic Features
Congenital disorders of glycosylation: Inverted nipples, lipodystrophy
Lysosomal storage disorders: I-cell disease Hurler-like phenotype
Hydrops fetalis
Lysosomal disordersMPS type I, IV A, & VIIGM 1 gangliosidosisGaucher diseaseNiemann Pick disease type CSialidosis Galactosialidosis Farber disease
Hematologic disordersGlucose-6-phosphate dehydrogenase deficiencyPyruvate kinase deficiencyGlucosphosphate isomerase deficiency
OthersCongenital disorders of glycosylationNeonatal hemochromatosisRespiratory chain disordersGlycogen storage disease type IV
Investi gati ons
Initial evaluation
Complete blood count Arterial blood gases and electrolytes Blood glucose Plasma ammonia Arterial blood lactate Liver function tests
Initial evaluation
Urine ketones if acidosis or hypoglycemia present
Urine reducing substances. Serum uric acid (low in molybdenum cofactor
deficiency).Plasma amino acids, quantitative
Laboratory studies if seizures present
Cerebrospinal fluid (CSF) amino acids
CSF neurotransmitters
Sulfocysteine in Urine
VLCFA
Lactate : pyruvate ratio: Respiratory chain defects
Complete blood cell count :
Neutropenia and
thrombocytopenia : Isovaleric
acidemia, methylmalonic
acidemia , and propionic
acidemia .
Neutropenia :Glycogen storage
disease type 1b Barth syndrome
and Pearson syndrome.
Serum electrolytes
& Blood gases
Acidosis/ alkalosis &
types
Anion gap ( organic
acidemias &
primary lactic
acidosis
High lactate
Euglycemia Hypoglycemia Euglycemia Hypoglycemia
Normal lactate
No ketosis
Ketosis +
Metabolic acidosis
MSUD Organic aciduria
PC deficiency,
HCS deficiency
GSD1, Gluconeogenesis defects, Respiratory
chain defects
NEXT
SLIDE
HypoglycemiaEuglycemia
High lactate Normal lactate
No ketosis
FAO defectPDH deficiency Renal tubular acidosis
Hyperammonemia
Metabolic acidosis Respiratory alkalosis
Plasma citrulline
Organicaciduria,
FAO defects, Primary lactic
acidosis
Urea cycle defects
Plasma citrulline
Low Normal High
Urine orotic acid
Elevated
Plasma ASAPlasma arginine
Normal Normal Normal Elevated Elevated
OTC deficiency
CPS deficiency
NAGS deficiency
Arginase deficiency
HHH ASL deficiency
ASS deficiency
Liver function tests
Galactosemia
Tyrosinemia
Alpha-1-antitrypsin deficiency
Neonatal hemochromatosis
mitochondrial respiratory chain disorders
Niemann-Pick disease type C.
Urine-reducing substances, ketones & pH
Clinitest reaction :galactose and glucose, but not fructose
Clinistix reaction (glucose oxidase) specific for glucose
pH <5 indicate IEM
Ketonuria is abnormal in neonates
Dinitrophenylhydrazine :α-ketoacids in MSUD.
Plasma carnitine and acylcarnitine profile
Elevation of carnitine esters Fatty acid oxidation defectsOrganic acidemiasKetosis
low carnitine levelsDisorders of carnitine biosynthesisPreterm infants and neonates receiving total
parenteral nutrition without adequate carnitine supplementation.
Secondary carnitine deficiency.
Second line investigations• To be performed in a targeted manner
Gas chromatography mass spectrometry of urineOrganic acidemias.
Plasma amino acids and acyl carnitine profile: by tandem mass spectrometryOrganic acidemias Urea cycle defectsAminoacidopathies Fatty acid oxidation defects.
High performance liquid chromatography :Quantitative analysis of amino acids in blood
and urineOrganic acidemias and aminoacidopathies
Lactate/pyruvate ratio- in cases with elevated lactate.
Urinary orotic acid- in cases with hyperammonemia for classification of urea cycle defect.
Enzyme assay: This is required for definitive diagnosis, but not available for most IEMbiotinidase assay- biotinidase deficiency
(intractable seizures, seborrheic rash, alopecia)GALT (galactose 1-phosphate uridyl transferase )
assay- galactosemia (hypoglycemia, cataracts, reducing sugars in urine).
Neuroimaging: MRI
IEM may be associated with structural malformations e.g. Zellweger syndrome has diffuse cortical migration and sulcation abnormalities.
Neuroimaging: MRI
Agenesis of corpus callosum : Menke’s diseasePyruvate decarboxylase deficiency Nonketotic hyperglycinemia
Neuroimaging: MRI
Glutaric aciduria type II: frontotemporal atrophy, subdural hematomas
Neuroimaging: MRI
MSUD: brainstem and cerebellar edema
Propionic & methylmalonic acidemia: basal ganglia signal change
Magnetic resonance spectroscopy : lactate peak elevated in mitochondrial disorders
leucine peak elevated in MSUD.
Electroencephalography (EEG):
Comb-like rhythm suggests MSUD
Burst suppression in NKH and holocarboxylase synthetase deficiency
Other investigations
Plasma very long chain fatty acid (VLCFA) levels: elevated in peroxisomaldisorders.
Mutation analysis when available.
CSF aminoacid analysis: CSF Glycine levels elevated in NKH.
Collecting samplesShould be collected before specific treatment
is started or feeds are stopped
Samples for blood ammonia and lactate should be transported in ice and immediately tested.
Lactate sample should be arterial or central line and should be collected after 2 hrs fasting in a preheparinized syringe.
Collecting samples
Ammonia sample is to be collected approximately after 2 hours of fasting in EDTA vacutainer. Avoid air mixing.
Sample should be free flowing.
Detailed history including drug details should be provided to the lab. (sodium valproate therapy may increase ammonia levels).
Metabolic autopsy
Samples to be obtained in infant with suspected IEM when diagnosis is uncertain and death seems inevitable
Blood: 5-10 ml; frozen at -200C; both heparinized (for chromosomal studies) and EDTA (for DNA studies)
Urine: frozen at –20oC
CSF: store at –20oC
Skin biopsy: including dermis in culture medium or saline with glucose. Store at 4-80C. Do not freeze.
Liver, muscle, kidney and heart biopsy: as indicated.
Clinical photograph (in cases with dysmorphism)
Infantogram (in cases with skeletal abnormalities)
MANAGEMENT OF INFANT AT RISK FOR A METABOLIC DISORDER
When a sibling has had symptoms consistent with a metabolic disorder, or has died of a metabolic disorder:
Before or during subsequent pregnancy
Prenatal discussion of possible diagnoses, and the parents and relatives should be screened for possible clues.
Old hospital charts and postmortem material should be reviewed.
When a diagnosis is known, intrauterine diagnosis to be tried.
The new baby should be delivered in a facility equipped to handle potential metabolic or other complications.
Initial evaluation includes a careful physical examination for the signs of IEM
All nonmetabolic causes of symptoms should be excluded.
The newborn screening program should be contacted for the results of the screening and for a list of the disorders screened.
Blood and urine tests before starting treatment for metabolic disease.
The specimens can be frozen (plasma, urine) and analysis performed later.
Enzyme assay of red blood cells, or enzyme and DNA analysis of white blood cells, fibroblasts, or liver tissue may be done for confirmation of diagnosis.
DNA analysis can sometimes be performed on a dried blood specimen (Guthrie blood spot).
In most cases, treatment needs to be instituted empirically without a specific diagnosis.
The metabolic screen helps to broadly categorize the patient’s IEM (e.g. urea cycle defect, organic academia, congenital lactic acidosis etc).
TREATMENT
Aims of treatment
Decreasing substrate availability (by stopping feeds and preventing endogenous catabolism)
To provide adequate calories
To enhance the excretion of toxic metabolites.
To institute co-factor therapy for specific disease and also empirically if diagnosis not established.
Supportive care- treatment of seizures (avoid
sodium valproate – may increase ammonia
levels)
maintain euglycemia and normothermia
fluid, electrolyte & acid-base balance
treatment of infection
mechanical ventilation if required.
Management of hyperammonemia
Discontinue all feeds. Provide adequate calories by intravenous
glucose and lipids. Maintain glucose infusion rate 6- 8mg/kg/min.
Start intravenous lipid 0.5g/kg/day (up to 3g/kg/day).
After stabilization gradually add protein 0.25 g/kg till 1.5 g/kg/day.
Dialysis is the only means for rapid removal of ammonia, and hemodialysis is more effective and faster than peritoneal dialysis. Exchange transfusion is not useful.
Sodium benzoate (IV or oral)- loading dose 250 mg/kg then 250-400 mg/kg/day in 4 divided doses. (not available in India).
L-carnitine (oral or IV)- 200 mg/kg/day
Sodium phenylbutyrate (not available in India)-loading dose 250 mg/kg followed by 250-500 mg/kg/day.
L-arginine (oral or IV)- 300 mg/kg/day (Intravenous preparation not available in India)
Suspected organic acidemia• Acute management The patient is kept nil per orally and
intravenous glucose is provided. Supportive care: hydration, treatment of
sepsis, seizures, ventilation. Carnitine: 100 mg/kg/day IV or oral. Treat acidosis: Sodium bicarbonate 0.35-
0.5mEq/kg/hr (max 1-2mEq/kg/hr)
Biotin 10 mg/day orally.
Vitamin B12 1-2 mg/day I/M (useful in B12 responsive forms of methylmalonic acidemias)
Thiamine 300 mg/day (useful in Thiamine-responsive variants of MSUD).
If hyperammonemia is present, treat as above.
Congenital lactic acidosis Supportive care: hydration, treatment of sepsis,
seizures, ventilation. Avoid sodium valproate.
Treat acidosis: sodium bicarbonate 0.35-0.5mEq/kg/hr
(max 1-2mEq/kg/hr)
Thiamine: up to 300 mg/day in 4 divided doses.
Riboflavin: 100 mg/day in 4 divided doses.
co-enzyme Q: 5-15 mg/kg/day
L-carnitine: 50-100 mg/kg orally.
Refractory seizures with suspectedmetabolic etiology
Seizures despite 2 or 3 antiepileptic drugsPyridoxine 100 mg intravenously. oral 15
mg/kg/day.Despite pyridoxine.. give trial of biotin 10
mg/day and folinic acid 15 mg/day (folinic acid responsive seizures).
Rule out glucose transporter defect: measure CSF and blood glucose
Asymptomatic newborn with a History of sibling death with suspected IEM:
After baseline metabolic screen, start oral dextrose feeds (10% dextrose).
After 24 hours, repeat screen. If normal, start breast feeds. Monitor sugar, blood gases and urine ketones, blood ammonia 6 hourly.
Medium chain triglycerides (MCT oil) before starting breast feeds
After 48 hours, repeat metabolic screen. Obtain samples for TMS and urine organic acid tests.
Follow-up for the first few months
Long term treatment of IEM
Dietary treatment: phenylketonuria, maple syrup urine disease, homocystinuria, galactosemia, and glycogen storage disease Type I & III.
Special diets for PKU and MSUD are commercially available in the west can be imported.
Based on the amino acid content of some common food products available in India, a low phenylalanine diet for PKU and diet low in branched chain amino acids for MSUDcanbe made.
urea cycle disorders and organic acidurias require dietary modification (protein restriction)
Enzyme replacement therapy
ERT is now commercially available for some
lysosomal storage disorders.
Pompe’s disease (Glycogen storage disorder
Type II).
Cofactor replacement therapy
Thiamine: mitochondrial disorders thiamine responsive variants of MSUD PDH deficiency & complex I deficiency
Riboflavin: Glutaric aciduria Type I, Type II mild variants of ETF ETFDH complex I deficiency
Pyridoxine: 50% of cases of homocystinuria due to
cystathionine β-synthetase deficiency pyridoxine dependency with seizures xanthurenic aciduria primary hyperoxaluria type I Hyperornithemia with gyrate atrophy
Biotin: Biotinidase deficiency Holocarboxylase synthetase deficiency
Cobalamin: Methylmalonic academia Homocystinuria
Folinic acid: Hereditary orotic aciduria Methionine synthase deficiencyCerebral folate transporter deficiency hereditary folate malabsorptionKearns-Sayre syndrome
Prevention
• Genetic counselling and prenatal diagnosis: • Most of the IEM are single gene defects,
inherited in an autosomal recessive manner, with a 25% recurrence risk.
• The samples required are chorionic villus tissue or amniotic fluid.
Substrate or metabolite detection:Phenylketonuria Peroxisomal defects.
Enzyme assay: lysosomal storage disorders like Niemann-Pick
disease , Gaucher disease.DNA based (molecular) diagnosis:
Detection of mutation in proband/carrier parents
Neonatal screening Tandem mass spectrometry is used in some
countries for neonatal screening for IEM
Aminoacidopathies ( phenylketonuria, MSUD,
Homocystinuria, Citrullinemia, Argininosuccinic
aciduria, hepatorenal tyrosinemia) fatty acid
oxidation defects,
Organic acidemias (glutaric aciduria, propionic
acidemia, methylmalonic acidemia, isovaleric
acidemia).
The cost of this procedure is high
Test is highly sensitive, the specificity is relatively low; and there are difficulties in interpretation of abnormal test results in apparently healthy infants.
Commercially available formulations used in IEM
Pyridoxine Tab Benadon (40mg) (Nicholas Piramal), Inj Vitneurin (1 ampoule contains 50 mg pyridoxine), Tab B-long 100mg
Hydroxycobalamin (Vitamin B12) Inj Trineurosol (1000mcg/ml) (Tridoss Laboratories)
Thiamine :Tab Benalgis (75 mg) (Franco India)
Riboflavin :Tab Riboflavin (5 mg) (Shreya)
Biotin Tab Essvit (5mg, 10mg) (Ecopharma)
Carnitine Syrup L-Carnitor (5ml=500 mg), Tab L-
Carnitor (500 mg), Inj carnitor (1g/5ml) (Elder)
Folinic acid Tab Leukorin (15 mg) (Samrath)
Sodium Benzoate Satchet 20g (Hesh Co.)
Arginine ARG-9 Satchet (3g) (Noveau Medicament)
Coenzyme Q Tab CoQ 30 mg, 50 mg. (Universal
Medicare)
Thank you