Inborn errors of metabolism

Background

• Suspect in any sick neonate
• Newborn screening varies by state
• May present as late as early childhood

Diagnosis

Exam and history:

• Lethargic (2/2 hyperammonia encephelopathy)
• Nausea/vomiting
• Difficulty feeding
• Seizure
• Unusual odors
• Hypotonia

Work-Up

1. Ammonia
   1. Elevated ammonia is common finding
2. Chemistry
   1. May see hypoglycemia, metabolic acidosis
3. Lactate
4. Ketones

Differential Diagnosis

Sick Neonate

THE MISFITS

• Trauma
• Heart
  • Congenital heart disease
  • Hypovolemia
• Endocrine
  • hypoglycemia
  • Hypothyroidism
  • Congenital adrenal hyperplasia
• Metabolic
  • Sodium
  • Calcium
  • Glucose
• Inborn errors of metabolism
• Seizure
• Formula / feeding problems
  • Hyponatremia
  • Hypocalcemia
  • FPIES / Food protein-induced enterocolitis syndrome
• Intestinal Disasters
  • Duodenal atresia
  • Midgut volvulus
  • Necrotizing enterocolitis
  • Intussusception
• Toxin
• Sepsis

Treatment

1. Must stop catabolism and acculmulation of toxins/ammonia
2. IVF with Dextrose at 1-1.5x maintenace
3. Stop feeding
4. Dialysis (ammonia >500)
5. NaBicarb if acidotic
6. Consider L-carnitine in conjuction with specialist, as some diseases may respond (but has side effects)
7. If seizing: consider Vit B6/pyroxidine

See Also

• Neonatal Resuscitation