Porphyria cutanea tarda is the most common of the porphyrias, with significant cutaneous involvement. This form may be hereditary but far more frequently is due to an exogenous agent, such as alcohol, oestrogens, iron, antimalarials (high doses), hexachlorobenzene, and chlorinated phenols. Other predisposing factors include diabetes mellitus and hepatitis C. While patients do have photosensitivity, there is some delay between sun exposure and the development of the lesions and they actually complain of skin fragility and, conversely, may appear sun-tanned.
Other main clinical features include bullae and erosions on a background of normal skin with atrophic scars from healed previous lesions. Small milia may also be present. Patients may develop hypertrichosis and sclero-dermatous changes on the face. The diagnosis is made by history, clinical features and elevated urinary porphyrins and the treatment includes the discontinuation of exacerbating factors, phlebotomy or low-dose chloroquine, 125 mg twice a week.
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