Annular papules on the legs

These annular papules and plaques with brownish, raised, and advancing borders (fig 1) developed bilaterally on the lower legs of a man in his 60s. The lesions had been slowly increasing in size and number over two decades. His mother had similar lesions. A diagnosis of disseminated superficial porokeratosis was confirmed by skin biopsy, which revealed two foci of cornoid lamellae (thin columns of parakeratotic cells) at the periphery of the lesions. Porokeratosis is a group of benign, chronic progressive disorders of keratinisation, with undetermined cause. Sporadic and familial cases have been observed and several causative gene mutations have been identified.12 Triggering factors in people who are genetically predisposed include ultraviolet radiation and immunosuppression.1 Treatment is indicated if the lesions cause pruritus or cosmetic concern, but clearance of the disseminated lesions is not always possible.1 Porokeratosis lesions can transform into skin cancer, most commonly squamous cell carcinoma, so patients should…
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