Low serum vitamin D levels in patients with myasthenia gravis

•The autoantibody response in myasthenia gravis is T cell dependent.•The regulatory T cell has been shown functionally defective in MG patients.•The immune-regulatory effect of vitamin D is known to induce the regulatory T cells.•Plasma 25(OH)D levels were significantly lower in patients with MG patients. Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disease. Vitamin D has important roles both in the autoimmune response and in skeletal muscles. We investigated the levels of 1,25-dihydroxy vitamin D [1,25(OH)2D] and 25-hydroxy vitamin D [25(OH)D] in patients with MG and healthy subjects. MG patients were classified by disease stage, age of onset and treatment status whether or not to taking immunosuppressive agents. MG patients had lower plasma 25(OH)D levels (mean, 18.8 ± 8.4 ng/mL) than healthy controls (26.3 ± 6.1 ng/mL) (p