[Juvenile myasthenia gravis]

Juvenile myasthenia gravis is a chronic autoimmune disorder which occurs when serum antibodies combine with nicotinic acetylcholine receptors at the muscle membrane of the motor endplate imparing the neuromuscular transmission. It results in early muscle fatigability with progression to a complete paralysis during repetitive muscle contraction (movements) or steady muscle contraction (postures), and less common persistent paralysis at rest. The cranial nerves, mainly the one innervating the extraoccular and palpebral levator, are the most susceptible to permanent weakness and paralysis at rest. Initial clinical presentations are generalized, ocular and respiratory forms. The diagnosis is suspected through medical history of abnormal fatigability and corroborated by physical examination, repetitive nerve stimulation of an affected but not complete paralyzed muscle, correction of fatigability by the intravenous administration of acetylcholine esterase inhibitors, and by the presence of serum acetylcholine receptors antibodies (ACRA). The long term treatment is symptomatic (acetylcholine inhibitors) and etiopathogenic (immunosupresor drugs, plasmapheresis, intravenous gamma globulin and thymectomy. Spontaneous or post symptomatic and etiopathogenic treatment remissions occur from 1 to 10 years. Fatality is rare but children are at high risk during myasthenia crisis.