https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734680 Background: Vitamin D has been shown to be related to autoimmune diseases, such as multiple sclerosis and psoriasis. Correlations have been reported between vitamin D levels and prevalence and severity of other autoimmune disorders, and also between vitamin D therapy and disease improvement and remission. Case Report: This is a case report of a patient with severe and refractory myasthenia gravis (MG) who followed a “high-dose vitamin D treatment”, a massive-dose treatment (80 000 to 120 000 IU/day) promoted by a medical center in Brazil (but still not proven), and she had her first complete remission after this type of treatment with increased vitamin D serum levels (400 to 700 ng/mL). Conclusions: This case report may reinforce the reported correlation between vitamin D level and disease severity and introduces a possible new use for vitamin D as a potential target for treating autoimmune diseases. We recommend large, double-blind, placebo-controlled, randomized studies using high-dose vitamin D treatment for refractory autoimmune diseases to reliably assess this pharmacotherapy target for these diseases.