Paediatric myasthenia: A moving target.

A two-and-a-half-year-old boy presented to the emergency department with an upper respiratory tract infection and increasing breathing difficulties over the past 24 h. His health was normal until two months before presentation. Since then, his parents noticed progressive (although fluctuating) motor weakness, trouble chewing and swallowing as well as episodes of choking on his secretions. His speech deteriorated to monosyllables, and he had trouble walking and getting up off the floor. The boy’s ‘tiredness’ seemed substantially more noticeable in the evenings. A physical examination of the boy revealed moderate respiratory distress. Otherwise, the only remarkable physical signs included bilateral asymmetrical ptosis (his right eye appeared to be more affected than his left eye), and decreased facial movements with the inability to close his eyes and with his mouth hanging open. He was generally weak, hypotonic and could not rise from a lying position. His deep tendon reflexes were preserved. On admission, his respiratory status deteriorated to the point of requiring intubation for five days. A diagnosis of respiratory syncytial virus pneumonia was confirmed. Although his respiratory status improved, his weakness remained. Diagnostic evaluations included high acetylcholinesterase antibodies and a positive edrophonium test, resulting in transient reversal of the ptosis. During the next six months, the patient was treated with various combinations of pyridostigmine, intravenous immunoglobulin and corticosteroids, with only partial improvement. At three years of age, he underwent a thymectomy. Within one year, he was weaned off all medications (pyridostigmine and prednisone). Four years later, he remains in complete remission.