neurologic disorders
Myasthenia Gravis
Uncommon forms
Ocular myasthenia gravisinvolves only extraocular muscles. It represents about 15% of cases. Congenital myastheniais a rare autosomal recessive disorder that begins in childhood. It is not immune-mediated and results from presynaptic or postsynaptic abnormalities, including the following: Reduced acetylcholine resynthesis due to choline acetyltransferase deficiency End-plate acetylcholinesterase deficiency Structural abnormalities in the postsynaptic receptor Ophthalmoplegia is common in patients with congenital myasthenia. Neonatal myastheniaaffects 12% of infants born to women with myasthenia gravis. It is due to IgG antibodies that passively cross the placenta. It causes generalized muscle weakness, which resolves in days to weeks as antibody titers decline. Thus, treatment is usually supportive. 