MedGen

A type of weakness that occurs after a muscle group is used and lessens if the muscle group has some rest. That is, there is diminution of strength with repetitive muscle actions. [from HPO]

An abnormality of conjugate lateral gaze in which the affected eye shows impairment of adduction. The pathognomonic clinical sign of internuclear ophthalmoplegia is an impaired adduction while testing horizontal saccades on the side of the lesion in the ipsilateral medial longitudinal fascicule. [from HPO]

Paralysis of one or more extraocular muscles that are responsible for eye movements. [from HPO]

Myasthenia gravis (MG) is an autoimmune disease in which antibodies bind to acetylcholine receptors or to functionally related molecules in the postsynaptic membrane at the neuromuscular junction. The antibodies induce weakness of skeletal muscles, which is the sole disease manifestation. The weakness can be generalized or localized, is more proximal than distal, and nearly always includes eye muscles, with diplopia and ptosis. The pattern of involvement is usually symmetric, apart from the eye involvement, which is often markedly asymmetric and involves several eye muscles. The weakness typically increases with exercise and repetitive muscle use (fatigue) and varies over the course of a day and from day to day, often with nearly normal muscle strength in the morning (summary by Gilhus, 2016). [from OMIM]