Eosinophilic cellulitis induced by subcutaneous administration of interferon-β.

Eosinophilic cellulitis (EC) is described as erythematous plaques with perivascular and interstitial infiltration of eosinophils. EC is associated with various skin disorders, and occurs in adverse drug reactions to many medications (1). A previous report described a patient with EC who was found to have increased interleukin (IL)-5-producing circulating T cells (2), suggesting the coexistence of a signal transducers and activator of transcription (STAT) 6-mediated Th2 response. We describe here a case of EC induced by administration of interferon (IFN)-β. A 68-year-old man presented with a 10-year history of a black nodule on his forearm. physical examination revealed a black, erosive, dome-shaped nodule, 20 mm in diameter, on the extensor surface of his right forearm (Fig. 1A). Excisional biopsy showed a dense infiltration of spindle-shaped atypical cells with pigmentation from the papillary dermis to the deep dermis. Immunohisto-chemical staining revealed that these tumour cells were positive for HMB45, S-100 and MelanA, and negative for AE1/AE3. From these results, the patient was diagnosed with malignant melanoma. The tumour was resected with a 2.5-cm surgical margin. After surgical treatment, DAV-Feron therapy (dacarbazine, nimustine, vincristine intravenously and interferon-beta injected around the scar intracutaneously) was administered once a month, for 6 months. However, during the third cycle of combination therapy, the patient reported pruritic erythematous swelling around the IFN-β injection site on the right forearm (Fig. 1B). Biopsy specimens revealed a dense infiltration of eosinophils in the superficial and deep perivascular dermis, and in the subcuta-neous layer (Fig. 2A, B). Serum myelo peroxidase anti-neutrophil cytoplasmic antibodies (ANCA) were negative, and there were no clinical signs of asthma. From the above findings, Churg Strauss syndrome and eosinophilic vasculitis were excluded. Clobetasol propionate ointment 0.05% were administered twice a day, and the pruritic erythema disappeared a few days after treatment. To further investigate the immunological profiles of the infiltrating cells, immunohistochemical staining for pSTAT1 and pSTAT6 were carried out, and revealed that the infiltrating lymphocytes contained both pSTAT1 + and pSTAT 6 + cells (Fig. 2C, D). From the above data the patient was diagnosed with eosinophilic cel-lulitis caused by the subcutaneous administration of IFN-β. To prevent progression of the tumour, we continued to administer IFN-β. As expected, the administration of IFN-β caused pruritic erythematous swelling at the injection site every time, although the eruption was easy to control. DISCuSSIoN IFN-β is thought to play an important role in tumour suppression in malignant melanoma (3, 4). …