Frequency of Dimethyl Fumarate-Induced Lymphopenia among Omani Patients with Multiple Sclerosis

Objectives: Dimethyl fumarate (DMF) is known to cause lymphopenia when used to treat patients with multiple sclerosis (MS). However, research on DMF therapy in the Arab world, especially in Oman, is scarce. This study aimed to analyse the prevalence of lymphopenia among Omani patients with MS and their reasons for discontinuing DMF therapy.

Methods: In this retrospective study, the medical records of Omani patients with MS who were treated using DMF at two tertiary hospitals in Muscat, Oman, from February 2017 to February 2023 were reviewed. Their demographic, clinical and laboratory data were retrieved and analysed. Absolute lymphocyte count values at baseline and at the last follow-up, as well as the reasons for discontinuing DMF therapy, were collected. Descriptive and inferential statistical techniques were used for data analysis. Binary-logistic regression analysis was used to identify the risk factors for DMF-induced lymphopenia.

Results: A total of 64 Omani patients with MS were included in this study. The majority of the study participants (n = 40; 63%) were female. All included patients started DMF therapy at the mean age of 33 ± 7.7 years. After administration of DMF, 14 (21.9%) patients developed grades 1-3 of lymphopenia. The DMF therapy was discontinued for 23 (36.0%) patients, mainly in response to adverse events or confirmed pregnancy. Female gender was the only significant predictor of DMF-induced lymphopenia (P = 0.037).

Conclusions: Most Omani patients with MS had mild lymphopenia (grades 1-2). Early adverse events and pregnancy were the main reasons provided for discontinuing DMF therapy.