Keratosis lichenoides chronica and eruptive keratoacanthoma-like lesions in a patient with multiple myeloma

We describe a 72-year-old woman with a 13-year history of a lichenoid dermatitis, who developed multiple, papular keratoacanthoma (KA)-like lesions and few crater-like nodules on the extremities over a period of 6 months before our observation. Her medical history also recorded multiple myeloma diagnosed a few years before. The long-standing dermatosis was diagnosed, clinically, as keratosis lichenoides chronica (KLC), although, histologically, a lichenoid tissue reaction pattern was not evident. On the other hand, histology from papular and nodular lesions of recent onset was consistent with a possible early phase of KA and spinocellular carcinoma, respectively. Oral acitretin induced regression of KA-like lesions and improvement of KLC but had no effects on crater-like nodules, which required surgical excision. KLC is a chronic disorder of keratinization characterized by lichenoid hyperkeratotic papules arranged in a linear pattern, erythematosquamous plaques and seborrhoea-like dermatitis. We emphasize in our case the association between KLC and multiple possible KAs, never previously reported, and speculate that these two rare conditions may represent here a 'continuum' from a pathogenetic point of view.