Acute porphyrias and porphyric neuropathy
The porphyrias are a group of uncommon inherited metabolic disorders of heme biosynthesis. Acute porphyrias are specific types of porphyrias characterized by the presence of acute attacks that usually present with abdominal pain, psychiatric symptoms, and neuropathy. The nonspecific porphyria presentations, the complexity of heme biosynthesis, and difficulty in interpreting the laboratory tests make the diagnosis of porphyria challenging. Treatment of acute porphyria and avoidance of precipitating factors should be initiated early to prevent potentially severe long-term sequelae from nerve damage. Porphyric neuropathy is one such complication and is characterized by an axonal neuropathy with predominant motor involvement. Sensory neuropathy is also found but is less common. Although the exact pathophysiology of porphyric neuropathy remains uncertain, neural energy failure from heme deficiency and neurotoxicity from porphyrin precursors are probably the two main mechanisms. The understanding of porphyric neuropathy and manifestations of each type of porphyria along with timely implementation of appropriate tests can significantly assist in the diagnosis of these rare diseases.