Large cutaneous-subcutaneous infiltrates: a side effect of interferon beta injections

Interferon alpha and gamma have been used to treat several hepatic, hematological and oncological diseases for years. Recently, interferon beta has been introduced as a therapeutic agent in relapsing-remitting multiple sclerosis. A 41-year-old female patient with multiple sclerosis developed non-tender, palm-sized, cutaneous-subcutaneous, reddish infiltrates at the injection sites on her thighs after 8 weeks of treatment with subcutaneous interferon beta injections. Histopathology revealed a perivascular lymphoid infiltrate of the dermis and a subtle lobular lymphoid infiltrate of the subcutis. Interferon beta therapy was discontinued for 4 weeks. With topical corticosteroids,the skin lesions resolved. When subcutaneous injections were resumed at a reduced dose, only erythema around injection sites developed without induration or pain. Slight erythema and swelling at interferon beta injection site are frequent and rare cases of cutaneous necrosis have been described. However, no reports of large, painful, cutaneous-subcutaneous infiltrates after interferon beta therapy have been published