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.
- Confirm excess and pattern with protected urine and plasma porphyrins, adding faecal fractionation through a specialist laboratory; urine porphobilinogen is not the diagnostic test for PCT.
- Investigate iron status, liver tests and fibrosis, hepatitis C, HIV, alcohol, smoking, oestrogen exposure and HFE variants because treatment of acquired drivers prevents relapse.
- Preferred disease-directed therapy is specialist venesection, commonly about 450 mL every one to two weeks while haemoglobin and ferritin are monitored to a low-normal target without causing anaemia.
- Low-dose hydroxychloroquine 100 mg twice weekly is an alternative when venesection is unsuitable; ordinary daily rheumatology dosing can mobilise porphyrin too rapidly and injure the liver.
- Stop alcohol and unnecessary iron, review oestrogen and treat hepatitis C or HIV with the relevant specialist; do not stop necessary therapy without an agreed substitute.
- Use gloves, sleeves, shade and opaque physical barriers against visible violet light while porphyrins fall; ordinary UV sunscreen alone may not prevent blistering.
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.
- Assess FBC, iron indices, liver function and fibrosis, hepatitis C, HIV and HFE context and refer jointly to dermatology and a porphyria or liver service.
PCT is confirmed and venesection is feasible without limiting anaemia or vascular-access problems.
- Agree a specialist schedule, commonly removing about 450 mL every one to two weeks, with haemoglobin and ferritin checked often enough to prevent excessive depletion.
- Continue until the service's low-normal ferritin target and falling porphyrins indicate iron reduction, then stop rather than producing symptomatic deficiency.
- Follow skin fragility, porphyrins, ferritin and the treated hepatic driver over months, using maintenance venesection only for documented biochemical relapse or recurrent iron loading.