I read with great interest the article published in Neurología under the title “Epidemiology of myasthenia gravis in the province of Ourense (Galicia, Spain),” which reports that 85.1% of patients diagnosed with myasthenia gravis (MG) present vitamin D deficiency (< 30ng/mL).1 In recent years, growing emphasis has been placed on the importance of vitamin D due to its influence in several processes, such as immunity. Vitamin D is known to play a significant role in the homeostasis of calcium and phosphorus, in the regulation of functional hormones, and in the activation of regulatory T cells and B cells.2
Kang et al.3 observed that serum vitamin D levels were significantly lower in patients with MG than in healthy controls. Furthermore, an improvement in muscle weakness has been observed after cholecalciferol supplementation in patients with low vitamin D levels.4 However, the most remarkable finding is the report of a patient showing remission of recurrent MG after administration of megadoses of vitamin D (80000–120000 IU/day).5 Nevertheless, megadoses are reported to be harmful to health due to an increase in the risk of falls, and consequently the rate of fractures.6 A recent randomised controlled trial did not observe a clinically significant improvement in patients treated with vitamin D with respect to those receiving placebo; however, the dose administered was 800 IU/day, which is much lower than that reported in previous studies.7
It is currently unclear whether low serum vitamin D levels are associated with a higher risk of MG, as has been described in other such diseases as multiple sclerosis.8 Therefore, further studies are needed on the influence of vitamin D on the onset and progression of MG. We should also mention that between 42% and 82% of patients with MG experience central fatigue; even patients in remission or with mild symptoms show mild fatigue.9,10 As central fatigue seems not to improve with immunosuppressant treatment, it is important to establish the role of vitamin D in the fatigue perceived by these patients.9 Therefore, I agree with Kang et al.3 in recommending that healthcare professionals monitor vitamin D levels in patients with MG in order to maintain optimal serum concentrations.
FundingThis study received no funding of any kind.
Conflicts of interestThe authors have no conflicts of interest to declare.
