[Leser-Trélat sign associated with Sézary syndrome and transitional cell carcinoma of the bladder].

Leser-Trélat sign is characterized by the sudden onset and rapid growth in number and size of multiple seborrheic keratoses, in relation to an underlying neoplasm. It is sometimes accompanied by pruritus and often associated with acanthosis nigricans. We describe a 63-year-old man diagnosed with plaque-stage mycosis fungoides who, during phototherapy, developed severe erythema and generalized skin thickening (Figure 1) accompanied by severe pruritus. Based on the skin biopsies, computed tomography scan, and bone marrow aspirate culture, he was diagnosed with Sézary syndrome. At that time, more than 100 hyperpigmented, keratotic papules of 1 to 2 cm and soft to touch were observed on the trunk (Figure 1), even though these papules had not been present 1 month earlier. A biopsy of 1 lesion on the trunk showed seborrheic keratosis. A parallel study by the urology department showed transitional cell carcinoma of the bladder. Chemotherapy and bladder instillations with bleomycin were started, with the seborrheic keratoses disappearing completely (Figure 2) within 2 months. Based on all this history, the patient was diagnosed with Leser-Trélat sign that could have been related to either or both neoplasms. Because seborrheic keratoses and malignant tumors are 2 common diseases in elderly patients, some authors question the existence of this sign because they cannot rule out that coexistence of both is incidental. However, although seborrheic keratoses are a common condition in certain age groups, onset is not sudden. Various hypotheses have been proposed for the pathogenesis of LeserTrélat sign; all of them consider that the tumor might secrete a growth factor that stimulates the formation of these lesions and could explain the Letters to the Editor