Patterns of local site reactions to subcutaneous glatiramer acetate treatment of multiple sclerosis: a clinicopathological study.

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system. Glatiramer acetate (GA) is a commonly used immunomodulating drug. It is administered subcutaneously and is usually well tolerated; however, various local site reactions have been documented. To characterize the clinical and histopathological patterns of local site reactions in patients treated with GA. A retrospective case series of 12 patients with MS who experienced a local site reaction following treatment with GA. We recognized 3 distinctive clinical patterns: early lesions with erythematous urticarial plaques and nodules (EPN) (75%), and late lesions: lipoatrophy (16.6%) and morpheiform plaques (8.4%). Biopsies revealed that the EPN lesions were characterized by superficial and deep infiltrate with eosinophils and some neutrophils, while the lipoatrophy showed sparse chronic inflammatory infiltrate with delicate fibrosis. The morpheiform plaque showed mixed inflammatory infiltrate and fibrosis. Seven patients applied clobetasole propionate ointment and then switched to tacrolimus monohydrate 0.1% ointment for up to a month. This treatment was beneficial for all patients with EPN. GA can cause a spectrum of injection site reactions that can be classified into 3 distinct patterns based on their time frame, clinical picture and histological pattern. Topical treatment with a potent steroid and tacrolimus cream can alleviate the EPN response.