The Frequency of Lymphopenia in Omani Multiple Sclerosis Patients Treated with Dimethyl Fumarate at Sultan Qaboos University Hospital

Background Multiple sclerosis is a chronic auto-immune disease that affects the central nervous system and leads to inflammation and demyelination of the white matter initially and later the gray matter. Several DMTs are now used to treat MS patients with variable efficacy and safety profiles. One of the DMTs is dimethyl Fumarate (DMF) which is taken orally and known to cause varying degrees of lymphopenia in which ALC is below (1000 cells/μl). Several real-world studies analyzing the safety of DMF were done globally. This study aims to measure the frequency of lymphopenia among Omani MS patients treated with DMF at SQUH. Material(s) and Method(s) This was a retrospective study conducted at a single-tertiary center (SQUH). We reviewed the electronic medical records in HIS of Omani MS patients treated with DMF at SQUH from May 2018 to December 2021. Demographic, Clinical, and relevant laboratory data were collected and analyzed using SPSS. ALC values at baseline, in the last follow-up, or at discontinuation were collected and analyzed. Also, reasons for DMF discontinuation were recorded and analyzed. In addition, the Chi-square test was used to identify risk factors for DMF-induced lymphopenia. Result(s) Forty-one Omani MS patients used or are currently taking DMF at SQUH. Six patients (14.63%) developed lymphopenia after DMF administration. One patient (2.44%) developed grade-1 lymphopenia, and five patients (12.20%) developed grade-2 lymphopenia, while none of the Omani MS patients developed severe lymphopenia (≥ grade 3). Twelve patients (29.3%) discontinued the use of DMF. Adverse events were the most common reason for DMF discontinuation. No risk factors for DMF-induced lymphopenia were identified. Conclusion(s) The frequency of lymphopenia among Omani MS patients exposed to DMF was in the same range compared to other regional and international studies in which most cases developed mild lymphopenia (grades 1 and 2). However, severe lymphopenia is rarely reported in other studies but is not observed in our study. Early adverse events were the main reason for discontinuation. Therefore, we recommend slower titration of DMF and the use of symptomatic treatment early after DMF initiation. In addition, the treating neurologist needs to ensure that the MS patient is aware of potential side effects and how they are managed before initiating DMF to increase the patient's compliance. Multiple sclerosis is a chronic auto-immune disease that affects the central nervous system and leads to inflammation and demyelination of the white matter initially and later the gray matter. Several DMTs are now used to treat MS patients with variable efficacy and safety profiles. One of the DMTs is dimethyl Fumarate (DMF) which is taken orally and known to cause varying degrees of lymphopenia in which ALC is below (1000 cells/μl). Several real-world studies analyzing the safety of DMF were done globally. This study aims to measure the frequency of lymphopenia among Omani MS patients treated with DMF at SQUH. This was a retrospective study conducted at a single-tertiary center (SQUH). We reviewed the electronic medical records in HIS of Omani MS patients treated with DMF at SQUH from May 2018 to December 2021. Demographic, Clinical, and relevant laboratory data were collected and analyzed using SPSS. ALC values at baseline, in the last follow-up, or at discontinuation were collected and analyzed. Also, reasons for DMF discontinuation were recorded and analyzed. In addition, the Chi-square test was used to identify risk factors for DMF-induced lymphopenia. Forty-one Omani MS patients used or are currently taking DMF at SQUH. Six patients (14.63%) developed lymphopenia after DMF administration. One patient (2.44%) developed grade-1 lymphopenia, and five patients (12.20%) developed grade-2 lymphopenia, while none of the Omani MS patients developed severe lymphopenia (≥ grade 3). Twelve patients (29.3%) discontinued the use of DMF. Adverse events were the most common reason for DMF discontinuation. No risk factors for DMF-induced lymphopenia were identified. The frequency of lymphopenia among Omani MS patients exposed to DMF was in the same range compared to other regional and international studies in which most cases developed mild lymphopenia (grades 1 and 2). However, severe lymphopenia is rarely reported in other studies but is not observed in our study. Early adverse events were the main reason for discontinuation. Therefore, we recommend slower titration of DMF and the use of symptomatic treatment early after DMF initiation. In addition, the treating neurologist needs to ensure that the MS patient is aware of potential side effects and how they are managed before initiating DMF to increase the patient's compliance.