We report a child with a T-cell lymphoblastic lymphoma, and a widespread erosive mucocutaneous eruption, whose clinical and immunopathological features were consistent with a diagnosis of paraneoplastic pemphigus. Direct immunofluorescence showed deposition of C3 in the epidermal intercellular spaces, and in a linear pattern along the dermo-epidermal junction. Circulating autoantibodies binding in a pemphigus-like pattern to mouse urinary bladder epithelium were found. By Western immunoblotting, the patient's serum recognized two epidermal polypeptides with molecular weights of 210 and 190 kDa. No reactivity with the 230-kDa bullous pemphigoid antigen and the 250-kDa desmoplakin I antigen was found.