A 66-year-old Japanese woman visited our hospital with a complaint of multiple papules on her trunk and extremities. She had a past medical history of appendicitis and blood transfusion 40 years earlier. For the last 10 years, she had noticed multiple, gradually enlarging papulonodular lesions with surrounding erythema on her trunk and extremities. Physical examination revealed multiple, violaceous papules or nodules, less than 10 mm in diameter, with surrounding erythema on her trunk and extremities (Fig. 1). The results of routine laboratory examinations, including blood count, liver function, renal function, serum calcium, and lactate dehydrogenase, were within the normal range. The peripheral blood picture showed a small population of atypical lymphocytes below 1% of the total white blood cells. Human T-cell lymphotropic virus type I (HTLV-I) serology was positive. A microscopic examination of a biopsy specimen from a nodule on the abdomen demonstrated diffuse infiltration of large pleomorphic T cells in the upper and middle dermis, although highly atypical lymphocytes, so-called flower cells, could not be recognized. Infiltrating lymphocytes were positive for CD2, CD3, CD4, CD5, CD7, and CD45, but negative for CD8 and CD20, immunohistologically. Bone marrow biopsy also demonstrated the infiltration of lymphocytes expressing CD2, CD3, CD4, CD5, and CD7, but not CD25. Southern blot analysis of the infiltrating cells in the skin revealed an integration of HTLV-I proviral DNA in T cells. Clonal T-cell receptor γ gene rearrangement was detected in skin and bone marrow biopsies. No abnormal mass or bone defect was detected by chest or abdominal computed tomographic scanning, systemic gallium-67 citrate scintigraphy, or chest radiography. On the basis of these data, the patient was diagnosed with smouldering-type adult T-cell lymphoma/ leukemia. The patient was started on topical steroid and electron beam radiation therapy (27 Gy/14 days). Five days after the start of irradiation, she noticed multiple patches of edematous erythema appearing on the trunk and extremities (Fig. 2). As it was initially suspected that these newly emerging erythema multiforme or toxic eruptions were caused by irradiation, therapy was interrupted. Anti-herpes simplex virus antibody was not checked because no typical herpes simplex lesions were noticed. The patient was not taking any systemic drugs. A skin biopsy was taken from a representative lesion on the chest. The pathologic specimen showed epidermotropism, liquefaction degeneration in the basal layer, marked edema, and dense infiltration of mononuclear cells in the upper dermis. Infiltrating cells possessed abundant cytoplasm and large pleomorphic nuclei with distinct nucleoli (Fig. 3). These findings were consistent with the histopathologic findings of erythema multiforme, except for the atypical lymphoid cell infiltration. Immunohistochemical staining demonstrated that the phenotype of the skin-infiltrating cells was identical to that of the atypical cells in the initial lesions. As the eruptions did not disappear in spite of the interruption of radiation, total skin irradiation was restarted. After completion of therapy, both the erythema multiforme-like lesions and the initial adult T-cell lymphoma/leukemia nodules on the trunk and extremities had resolved, leaving brown pigmentation. The patient has been free of any recurrence of skin lesions or systemic symptoms for 6 years after the completion of total skin irradiation.
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