A 58-year-old lady presents with an episode of erythematous papulovesicular rash, which first appeared as weeping blisters on her back after an episode of sunburn when she was 18.

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<p>A 58-year-old lady presents with an episode of erythematous papulovesicular rash, which first appeared as weeping blisters on her back after an episode of sunburn when she was 18.</p><p>Over time, new lesions have developed on multiple body regions. She reports the condition worsens in summer.</p><p>She also reports experiencing dysuria and dyschezia. There is a significant family history, with her sister, nephew and father affected by similar skin lesions. </p><p>On examination, there are erythematous plaques with scaly crusts, symmetrically distributed on the chest and arms. The groin and inframammary folds are also involved.</p><p>These painful and pruritic lesions are clearly demarcated and thickened. </p><p>Erosions have resulted from the coalescence of lesions. The mucous membranes are spared.</p>

Professor Dedee Murrell is head of dermatology at St George Hospital, and conjoint professor at the University of NSW, Sydney.