[Two sisters with congenital myasthenic syndrome: case report]

To report two sisters with congenital myasthenic syndrome [CMS] masquerading as inyasthenia gravis. Two six and seven years old sisters presented with variable strabismus, ptosis, and fatigue. All symptoms were aggravated with exercise and improved with rest. Intramuscular prostigmin injection decreased their symptoms. A diagnosis of CMS was made according to early onset [infancy], familial pattern, and lack of serum antibodies. Oral neostigmine was begun for treatment. Although CMS is a rare disorder, they should be considered in all cases with variable strabismus and ptosis