Three cases of myasthenia gravis from one family with variations in clinical features and serum antibodies.

Myasthenia gravis, an autoimmune disorder affecting neuromuscular transmission, is mainly sporadic while familial cases are very rare. Usually familial myasthenia gravis cases have uniform clinical symptoms as well as serum anti-acetylcholine receptor antibodies. Interestingly, in our cases varying clinical types of myasthenia gravis and seropositive/seronegative anti-acetylcholine receptor antibodies coexisted in the same family. The mother and her daughter both had ocular myasthenia gravis, detectable anti-acetylcholine receptor antibodies and non-detectable anti-muscle-specific kinase antibodies, and good responses to medications. The son displayed ocular symptoms at the onset, and then progressed into a generalized form after 1 year. His serum anti-acetylcholine receptor antibodies and anti-muscle-specific kinase antibodies were both negative. Neither corticosteroids nor thymectomy alleviated his symptoms. Human leukocyte antigen DQA1*0301 allele sharing by the three patients may be involved in their genetic susceptibility to myasthenia gravis, and subtle differences in human leukocyte antigen DQB1 alleles may be associated with their variations in clinical features and serum antibodies.