From a Lancet review:

Hereditary porphyrias represent a group of 8 metabolic disorders of the haem biosynthesis. They are characterised by acute neurovisceral symptoms, skin lesions, or both.

Every porphyria is caused by abnormal function of a separate enzymatic step, resulting in a specific accumulation of haem precursors:

- 7 porphyrias are the result of a partial enzyme deficiency
- a gain of function mechanism is present in one new porphyria

Acute porphyrias present with acute attacks - severe abdominal pain, nausea, constipation, confusion, and seizure - and can be life-threatening.

Cutaneous porphyrias present with painful photosensitivity, skin fragility and blisters.

Porphyrias are still underdiagnosed. Screening of families to identify presymptomatic carriers and avoidance of precipitants is important.

Porphyrias. The Lancet, Volume 375, Issue 9718, Pages 924 - 937, 13 March 2010.

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