Synopsis
Recognise painless photosensitive hand fragility, confirm a porphyrin rather than acute-porphyria pattern, identify hepatic and iron drivers, and use venesection or low-dose hydroxychloroquine safely.
- Porphyria cutanea tarda causes painless skin fragility, vesicles and tense bullae on sun-exposed backs of hands and forearms, followed by crust, milia, scarring and pigment change.
- Facial hypertrichosis and hyperpigmentation can accompany the hand disease; erythema may be minimal and ordinary window glass does not block all porphyrin-activating visible light.
- Reduced hepatic uroporphyrinogen decarboxylase activity permits oxidised porphyrins to accumulate, circulate and absorb light energy in superficial skin vessels.
Key red flags
Painful inflamed blisters, extensive mucosal disease, neuropathy or abdominal crisis symptoms are atypical for porphyria cutanea tarda, while jaundice, weight loss, hepatomegaly, ascites or cognitive change requires expedited hepatic assessment.
Jaundice, ascites, hepatomegaly, splenomegaly, weight loss, bleeding or encephalopathy demands expedited liver assessment beyond routine PCT care.
Investigation priorities
Demonstrate substantial porphyrin excess using specimens protected from light.
Management branches
Painless sun-exposed hand fragility, bullae, milia or facial hypertrichosis suggests PCT.
- Document exposure distribution, trauma, urine colour, alcohol, smoking, oestrogen, iron, medicines and liver or neurovisceral symptoms and photograph representative lesions with consent.
- Send light-protected urine and plasma for porphyrin quantification and specialist fractionation, adding faecal analysis and acute porphobilinogen only when the laboratory or phenotype indicates.
PCT is confirmed and venesection is feasible without limiting anaemia or vascular-access problems.