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an approach to iem in pediatric pt.s
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Approach to Inborn Error of Metabolism in a Neonate
Filomena Hazel R. Villa, MD
PL2
Objectives
• To recognize IEM in a neonate with non-specific signs and symptoms
• To make use of simple lab tests in the diagnosis of IEM
• To know the initial management of life threatening conditions associated with IEM
Signs and Symptoms
• May be gradual
• May be sudden
• May be catastrophic
Signs and Symptoms
• Respiratory
• Cardiac
• GI
• Neurological
• Infectious disease
Categories of IEM
• Disorders of:
• Amino acids
• Carbohydrates
• Fatty acid
• Lysosomal and peroxisomal function
• Mitochondrial
• Organic acids
Presentation
• Metabolic acidosis
• Hyperammonemia
• Hypoglycemia
Metabolic acidosis
• pH <7.35
• Excess H+
• HCO3 deficit
• Calculate anion gap– Na – (Cl + HCO3)– Normal is 8-16meq/l
Metabolic Acidosis
• If Chloride is increased- HCO3 wasting
• GI or renal disorders
• If Chloride is Normal and
Anion gap is > = 16--- excess acid production
Metabolic acidosis
• Approach is to give Na HCO3
• If unresponsive to HCO3-- IEM
Hyperammonemia
• Normal ammonia level- < 50 umol/l
• > 200 -- IEM
• If within 24 hours of life; preterm, RD THAN
• After 24 hours- IEM
Hypoglycemia
• Glucose level helps in the differential diagnosis
STEPS:
• 1. Determine if there is metabolic acidosis
• 2. Is anion gap >16?
• 3. Is there hypoglycemia?
• 4. Is there hyperammonemia? – Within 24 HOL?– After 24 HOL?
Copyright ©1998 American Academy of Pediatrics
• Healthy NB rapidly ill, – Ketoacidosis, poor feeding
• Vomiting, dehydration• Hypotonia, lethargy• Tachypnea, seizures• Coma, unusual odors
Organic acidemia
Organic acidemia
• Labs:
• Urine organic acids
• Ketonuria (in the NB)- pathognomonic of IEM
• Neutropenia, thrombocytopenia
• +/- hyperammonemia
• Abnormal acylcarnitine
• Treatment:
• Stabilize
• Get rid of organic acid intermediates, and ammonia- hemodialysis
• Carnitine
• After stabilization, may resume oral feeds
• Consult dietitian, and metabolic specialist
Organic acidemia
Urea cycle disorder
• No acidosis (respiratory alkalosis)
• No ketones (unlike organic acidemia)
• No hypoglycemia
• But with hyperammonemia
• Treatment:• Remove ammonia• Hydration with D10 + electrolytes• D/C all protein x 24 hours—calories from CHO
and fat• Na phenylacetate/Na benzoate• Give arginine• Protein restriction for life
Urea cycle disorder
• Prognosis: guarded
• Even with Treatment, many will die
• Definitive treatment: liver transplant
Urea cycle disorder
Summary
• Metabolic acidosis + hyperammonemia
• Request for specific lab studies
• Consult metabolic specialist
• Initial therapy- stabilize patient!
• Long term treatment- based on specific IEM
Thank you !