Low Doses of Intravenous Immunoglobulin as a Successful Treatment in Rituximab-induced interstitial pneumonitis among Multiple Sclerosis Patients: A Case Series Study (PP-38)

                       
Background: Rituximab, an anti-CD20 monoclonal antibody, has resulted in significant advancements in enhancing disease management and treatment of multiple sclerosis (MS). Therefore, this therapeutic agent has been employed frequently in treating MS patients. Nevertheless, increased use of rituximab has been related to hypersensitivity reactions such as interstitial pneumonitis. Only a few cases of rituximab-associated interstitial pneumonitis have been reported, highlighting the rarity of this hypersensitivity in rituximab therapy.
 
Case presentation: We present a case series of interstitial pneumonitis in four patients (one neuromyelitis optica spectrum disorder (NMOSD) and three multiple sclerosis (MS) patients) treated with rituximab who responded to low doses of intravenous immunoglobulin (IVIG). Most of the patients presented with low-grade fever, myalgia, cough, generalized weakness, and low O2 blood saturation. The neurological status was stable, and no new-onset neurological manifestations were noticed. The imaging examination revealed ground-glass opacities and consolidation, which suggested the diagnosis of pneumonitis. The computed tomography scan with pulmonary thromboendarterectomy protocol exhibited no abnormalities. In addition, no alterations in magnetic resonance imaging parameters were found during the examination. All laboratory findings except for high erythrocyte sedimentation rate and C-reactive protein levels were normal. The polymerase chain reaction test of COVID-19 was negative. The administration of antibiotics did not improve the patient’s clinical manifestation. Considering the above clinical findings, the infectious disorders were ruled out. Afterward, the patients received low doses of IVIG (30 g) treatment, and significant improvement in clinical manifestations was observed in MS patients. However, the NMOSD patient did not improve with the administration of IVIG.
 
Conclusion: Interstitial pneumonitis, as a hypersensitivity reaction, is an important adverse effect of rituximab. IVIG, despite low doses, can be a valuable treatment choice for patients under treatment for rituximab who present with clinical manifestations of interstitial pneumonitis.