Inborn errors of metabolism

Background

• Over hundreds of diseases
• Suspect in any sick neonate
• Newborn screening varies by states, California tests for 29 major diseases
• May present as late as early childhood

Diagnosis

Exam and history:

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

Work-Up

1. Elevated Ammonia
   1. Key to suspect diagnosis, however there are a few diseases where ammonia may be normal
2. +/- Hypoglycemia, metabolic acidosis, anion gate, elevated lactate, ketones
3. Sepsis work up usually concomitant, if patient is ill as these children are prone to infections

DDx

in neonates: THE MISFITS (see Neonatal Resuscitation)

Treatment

1. Must stop catabolism and acculmulation of toxins/ammonia
2. IVF with Dextrose at 1-1.5x maintenace
3. Don't feed
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. Antibiotics-- assume sepsis
8. if seizing-- consider Vit B6/pyroxidine

See Also

see Neonatal Resuscitation