A 31-year old man presented with swelling and purpura of the dorsum of the hands following sun exposure. There was a preceding lifelong history of photosensitivity, but this episode, which occurred after the recent commencement of oral iron therapy, and after recent alcohol ingestion, was much more severe than any preceding episode. Skin biopsy performed 48 h after the onset of symptoms showed features consistent with the early stages of leukocytoclastic vasculitis. Direct immunofluorescence showed homogeneous thick staining of the vessel walls with IgG, IgM and IgA, together with abundant perivascular fibrinogen. A subsequent periodic acid-Schiff (PAS) stain on the skin biopsy revealed thickening of the walls of dermal vessels, which was not discernible in routinely stained (hematoxylin/eosin) sections. The diagnosis of erythropoietic protoporphyria (EPP) was confirmed by significantly elevated erythrocyte protoporphyrin levels and positive plasma fluorimetry. The diagnosis of porphyria may have been missed by routine skin microscopy if not for the additional information provided by clinical history, direct immunofluorescence and PAS stain. The pathogenesis and histopathology of acute and chronic vascular changes in EPP are reviewed. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.