Porphyria

- Porphyrias are group of inherited disease resulting from deficiencies in haem biosynthetic pathway
- Acute porphyrias : acute intermittent porphyria, variegate porphyria, hereditary coproporphyria
- Non acute porphyria : cutaneous hepatic porphyria, congenital porphyria, erythropoeitic protoporphyria
- precipitants of acute attacks are: stress, infection, pregnancy, menstruation, starvation, drugs (sulphonamides, barbiturates, phenytoin)
- Haematin can help as it acts as negative feedback operator on the porphyrin synthetic pathway
- enzyme inducer exacerbate porphyria as they induce the pathway
- Ehrlich's test: add one volume of Ehrlich reagent to one volume of urine and urine turns red. Add two volumes of chloroform and red colour stays in upper layer
- Variegate porphyria is associated with raised urinary & fecal protoporphyrins
- Hereditary coproporphyria is associated with raised urinary & fecal coproporphyrins

Essential MRCP facts about porphyria
- All porphyrias have autosomal dominant inheritance except congenital porphyria
- Only acute porphyrias develop neurological consequence (ALA is neurotoxic)
- All porphyrias are photosensitive, except acute intermittent porphyria
- If the name sound's "inherited" eg.congenital porphyria or hereditary coproporphyria, then it is extremely rare.







Porphyria cutanea tarda
- most common subtype of porphyria
- deficient activity of enzyme uroporphyrinogen decarboxylase, causing accumulation of uroporphyrinogen III
- most common presenting sign is fragility of sunexposed skin after mechanical trauma, leading to erosion and bullae on dorsal hand, forearm and face
- diagnosis is by increased plasma and urinary porphyrins
- treatment: chloroquine, venesection