Anti-Musk Positive Myasthenia Gravis and Three Semiological Cardinal Signs.

Myasthenia gravis (MG) is a relatively uncommon disorder with an annual incidence of approximately 7 to 9 new cases per million. The prevalence is about 70 to 165 per million. The prevalence of the disease has been increasing over the past five decades. This is thought to be due to better recognition of the condition, aging of the population, and the longer life span of affected patients. MG causes weakness, predominantly in bulbar, facial, and extra-ocular muscles, often fluctuating over minutes to weeks, in the absence of wasting, sensory loss, or reflex changes. The picture of fluctuating, asymmetric external ophthalmoplegia with ptosis and weak eye closure is virtually diagnostic of myasthenia. We report an atypical MG case with three semiological cardinal signs.