AbstractObjectiveThe aim of this study was to assess the clinical efficacy of long‐term (>6 months) oral fumarate maintenance treatment regimen and to determine its adverse effect profile.BackgroundWe previously showed the efficacy of oral fumarate treatment in psoriasis. However, little is known about long‐term maintenance therapy with oral fumarates. Because of concern about renal toxicity and/or other potentially hazardous adverse effects, their role in the long‐term management of psoriasis is still controversial and limited.MethodsClinical data and laboratory parameters of 83 psoriasis patients who were treated with oral fumarates during an uninterrupted period of 6 or more months, were collected and subsequently analysed.ResultsIn 31 of the 83 patients the oral fumarate therapy was discontinued preliminarily (<6 months) because of intolerable adverse effects (9 patients), lack of clinical efficacy (16 patients), insurance refunding problems (4 patients) and lost to follow‐up (2 patients), A major improvement of the psoriasis was present in 41 of the 83 patients. Long‐term oral fumarate maintenance therapy was accompanied by subjective adverse effects, mainly flushing (28 patients) and gastrointestinal upset (15 patients) and by a relative lymphocytopenia (35 patients).ConclusionOral fumarates are effective well tolerated drugs suitable for long‐term management of psoriasis. However, this systemic therapy still has to be considered experimental and should only be performed under strictly controlled conditions. The cause and the clinical relevance of the relative lymphocytopenia, which occurs in a high percentage of patients during long‐term oral fumarate maintenance treatment regimen are unknown and still have to