MuSK not MNGIE: Atypical MuSK-antibody myasthenia presenting as a genetic disorder.

Myasthenia gravis is a treatable autoimmune disease caused by autoantibodies directed against membrane proteins at the neuromuscular junction. While acetylcholine receptor antibodies are most common, a minority of patients have antibodies directed against muscle-specific kinase (MuSK-antibody). Differentiating features often include subacute onset and rapid progression of bulbar, respiratory and neck extensor muscles, with sparing of distal appendicular muscles, most commonly in middle-aged females.