Persisting lymphopenia and dimethyl fumarate: A clinical commentary.

Severe prolonged lymphopenia as rare side-effect of dimethyl fumarate is mostly reversible. Caldito et al. report a case of persistent severe lymphopenia over 5 years after discontinuation of dimethyl fumarate. We discuss several clinical implications. Safe withdrawal of disease modifying therapies in terms of reoccurrence of disease activity and drug related adverse events need further attention as our treatment armamentarium continues to grow.