In patients with severe abdominal pain, dark or reddish urine, systemic arterial hypertension, tachycardia, and constipation, the possibility of acute porphyria should be considered. Unfortunately, all of these symptoms occur in other more common conditions, and the diagnosis of porphyria is often overlooked. The diagnostic study of choice is the measurement of 5-aminolevulinic acid (ALA) and porphobilinogen in urine or serum. There are four types of porphyria, and all are due to deficiencies of one or more of the enzymes required for normal heme synthesis. Most types of porphyria are inherited, although the most common type, porphyria cutanea tarda, is usually an acquired disorder associated with liver disease and iron overload.
Q: What is the differential diagnosis of rapidly progressive weakness?
A: The differential diagnosis of rapidly progressive weakness is broad and includes myelopathy, myasthenia gravis, Guillain–Barré syndrome, vasculitic polyneuropathy, neoplastic polyradiculoneuropathy (Eaton–Lambert syndrome), acute porphyria, lead poisoning, arsenic or shellfish ingestion, thallium, hypokalemia, hypomagnesemia, and hypophosphatemia.
Q: Why are the acute porphyrias more common in women than in men?
A: Female sex hormones, particularly progesterone, are porphyrogenic; thus, the acute porphyries are more often clinically manifested in women than in men, and it is rare for symptoms to develop before puberty.
New England Journal of Medicine - Vol. 358, No. 26, June 26, 2008