Vitamin D deficiency in patients with myasthenia gravis and improvement of fatigue after supplementation of vitamin D3: a pilot study.

BACKGROUND Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disorder. Vitamin D has important roles both in the autoimmune response and in skeletal muscles. We determined the levels of 25-hydroxy vitamin D [25(OH)D] in patients with MG and in healthy subjects to determine whether vitamin D deficiency is present in MG and whether vitamin D supplementation has beneficial effects on fatigue. METHODS Plasma levels of 25(OH)D were analyzed in 33 patients with MG (22 males; mean age, 58 years) and in 50 healthy age- and sex-matched blood donors, without vitamin D3 medication. MG composite (MGC) score assessed fatigue. Thirteen patients with MG without previous vitamin D3 supplementation were started on vitamin D3 supplementation (cholecalciferol) 800 IU/day, with a follow-up examination after 2.5-10 months (mean, 6 months). RESULTS Patients with MG without pre-existing vitamin D3 supplementation (N = 16) had a mean MGC of 4.5 and lower plasma 25(OH)D levels (mean, 51 ± 19 nM) than healthy controls (69 ± 21 nM) (P = 0.017). Seventeen patients had pre-existing vitamin D3 supplementation, because of corticosteroid treatment, and their mean 25(OH)D was 79 ± 22 nM and mean MGC was 5.5. In the 13 patients who received cholecalciferol, 25(OH)D was overall increased at follow-up with 22% (P = 0.033) and MGC score improved by 38% (P = 0.05). CONCLUSIONS Plasma 25(OH)D levels are significantly lower in patients with MG compared with healthy controls. As vitamin D has beneficial effects on the autoimmune response and on fatigue score in patients with MG, we suggest monitoring this parameter in patients with MG and supplementation with vitamin D3 when 25(OH)D levels are low.