Early predictive risk factors for dimethyl fumarate-associated lymphopenia in patients with multiple sclerosis.

Background: Lymphopenia is a major concern in MS patients treated with dimethyl-fumarate (DMF) as it increases the risk of progressive multifocal leukoencephalopathy. A pronounced reduction in absolute lymphocyte counts (ALCs) early after treatment initiation has been suggested to be associated with the occurrence of lymphopenia thereafter.

Objectives: To identify risk factors for DMF-induced lymphopenia and evaluate whether the degree of decrease in the ALCs three months after initiation of DMF treatment is a predictor of the subsequent development of lymphopenia.