Acute intermittent porphyria

Background

• Related to defect(s) in heme synthesis causing a buildup of porphyrins
• Autosomal dominant, but poor penetrance

Clinical Features

• Hallmark is abdominal pain with otherwise negative workup
• May develop neurological symptoms - paresthesias, weakness. May progress to bulbar involvement and need for respiratory support/intubation.

Triggers

• Infection, metabolic stress
• Carbohydrate deficiency
• Tobacco, EtOH

Diagnosis

• Unlikely to diagnose first episode in ED given rarity of disease
• Can check spot urine porphobilinogen (PBG) - sendout at most hospitals

Management

• Analgesia
• Avoid offending meds
  • Most seizure meds contraindicated. Benzodiazepines, gabapentin, levetiracetam, and vigabatrin OK
  • Avoid reglan
• Glucose load
  • Decreases porphyrin production
  • Typical protocol is D10W 3-4 liters daily x 4 days
  • Risk of hyponatremia given significant free water load
• Hemin
  • Decreases porphyrin production, significantly more potent than glucose
  • Recommended for most cases requiring hospitalization, or any with neurologic symptoms
  • 3-4 mg/kg daily for 4 days
  • Can cause significant infusion site phlebitis - minimize by reconstituting in 25% albumin; consider central venous administration
  • Very expensive - around $8000 per 313 mg vial

Disposition

• Admit all but very minor attacks

External Links

http://www.porphyriafoundation.com/