Porphyrias

1. Big picture

Porphyrias are rare disorders of heme synthesis. They are important in the final exam because they can mimic common diseases:

Severe recurrent abdominal pain + normal abdominal exam + tachycardia/hypertension + neuropathy/psychiatric symptoms + hyponatremia
        ↓
think acute hepatic porphyria, especially acute intermittent porphyria

The two most exam-relevant porphyrias are:

1. Acute intermittent porphyria (AIP) — acute neurovisceral attacks, abdominal pain, autonomic symptoms, neuropathy, psychiatric symptoms; usually no photosensitivity.
2. Porphyria cutanea tarda (PCT) — chronic photosensitive blistering skin disease, liver/iron association; usually no acute abdominal-neurologic attacks.

A practical internal medicine rule:

Acute abdomen without clear organic cause + neurological/autonomic signs → urine porphobilinogen.
Fragile blistering skin on sun-exposed areas + liver/iron/alcohol/HCV risk → plasma/urine porphyrins.

GeneReviews describes an acute porphyria attack as elevated urine porphobilinogen with neurovisceral manifestations lasting >24 hours and no better explanation; attacks usually begin in early adult life and are more common in women. ([NCBI][1])

---