Erythema Ab Igne with Histological Features of Keratosis Lichenoides Chronica

Erythema ab igne (EAI) is a localized, hyperpigmented and reticulated dermatosis at sites of chronic heat exposure. Within longstanding skin lesions of EAI, hyperkeratotic lesions may emerge and can potentially transform into pre-malignant or malignant skin lesions. A 55-year-old woman presented for the evaluation of multiple hyperkeratotic lesions along with a reticular patterned hyperpigmentation on her right knee, an area that had repeated and prolonged exposure to a heat source over a period of several months. Based on her clinical history and the physical examination of her lesions, she was diagnosed as having a hyperkeratotic form of EAI. A skin biopsy was performed to rule out malignant alteration, but the histopathological findings were supportive of keratosis lichenoides chronica.