Short-term effect of low-dose rituximab on myasthenia gravis with muscle-specific tyrosine kinase antibody.

Abstract

The study aims to investigate the short-term efficacy of low-dose rituximab and its effect on immunological biomarker levels in myasthenia gravis (MG) patients with antibodies against muscle-specific tyrosine kinase (MuSK-MG). Twelve MuSK-MG patients were enrolled in this prospective, open-label, self-controlled pilot study. Clinical severity was evaluated at baseline and 6mo after a single rituximab treatment (600 mg). B lymphocyte subtypes, MuSK antibody titers, together with levels of immunoglobulins, serum B-cell activating factor (BAFF), a proliferation-inducing ligand (APRIL), soluble CD40L, and four exosomal microRNAs were evaluated. A correlation matrix to reveal pairwise relationships among above variables was also generated. The single rituximab treatment significantly lowered the clinical severity scores and reduced daily dosage of prednisone (P=.032) at 6mo. MuSK antibody titers decreased (P=.035) without significant changes in immunoglobulin levels. Serum BAFF level increased (P=.010), which negatively correlated with the percentages of B cells in lymphocytes as well as clinical severity. Additionally, serum exosomal miR-151a-3p showed a reduction of 28.1% (P=.031). We confirmed the clinical efficacy of low-dose rituximab in MuSK-MG, accompanied by a decrease in MuSK antibody titers and an increase in serum BAFF. Serum BAFF levels negatively correlated with B-cell counts as well as clinical severity.