PCT, the commonest porphyria, is the only type that may be either sporadic (80% of
cases) or familial (AD). Reduced activity of uroporphyrinogen decarboxylase results in
overproduction of photoactive porphyrins. Uroporphyrinogen decarboxylase is
inactivated by an iron-dependent process that is not fully understood, but a variety of
factors can initiate disease.
Water-soluble porphyrins cause skin fragility and blistering on exposed skin.
Uroporphyrin also stimulates fibroblasts to produce collagen in the skin, and this may
explain some of the cutaneous features.
What should I look for?
PCT only affects the skin and is commonest in men. The presentation is subacute, and the
relationship to sun exposure may be missed.
• Skin fragility: minor knocks produce erosions on the dorsum of the hands.
• Itching or burning may precede blisters on sun-exposed skin.
• Haemorrhagic vesicles, bullae, and crusted erosions, most often affecting exposed skin
on the dorsum of the hands, face, and upper chest.
• Superficial scars or milia (firm, white, pinhead-sized papules—sequelae of
subepidermal blisters).
• Dystrophic calcification.
• Hypertrichosis usually starts on the temples and affects the cheeks and/or forehead.
• Blisters beneath the nail plate; painful discoloration (yellow, blue, or haemorrhagic) of
the nail; loss of the lunula, onycholysis, or dystrophy.
• Diffuse or reticulated hyperpigmentation of sun-exposed skin.
• Waxy, yellowish thickening of sun-exposed skin (‘sclerodermoid’).
• Normal teeth (unlike congenital erythropoietic porphyria).
• Normal mucosa (involved in some autoimmune blistering diseases).
What should I do?
• Confirm the diagnosis, and exclude pseudoporphyria by measuring porphyrins in fresh
samples of urine and stool. Fresh urine containing excess uroporphyrins is pink and
fluoresces bright coral pink under UVA light (Wood light).
• Biopsy a fresh blister for histology: subepidermal cell-poor blister, periodic acid–Schiff
(PAS)-positive glycoproteins at the BMZ and around blood vessels, and, for direct IMF,
Igs deposited at the BMZ and around blood vessels.
• Exclude risk factors, including hepatitis C.
• Withdraw precipitating factors, including alcohol and oestrogens.
• Advise strict sun protection.
• Regular venesection (400–500mL every 2 weeks for 3–6 months) depletes iron stores.
Alternatively, desferrioxamine can be helpful.
• Consider prescribing low-dose hydroxychloroquine (100–125mg x2/ week)—higher
doses may cause hepatitis.
• Monitor for the development of hepatocellular carcinoma.