Which tissue is afflicted by Myasthenia gravis?

Which of the following disorders is a genetic disorder?

$A$: Inflammation of a skeletal joint may immobilize the movements of the joint.
$R$: Uric acid crystals in the joint cavity and ossification of articular cartilage lead to this.

Choose the correct pair.

Select the correct statement regarding the specific disorder of the muscular or skeletal system.

$A:$ Myasthenia gravis is a protozoan caused disorder.
$B:$ It is affecting the neuromuscular junction leading to fatigue,weakening and paralysis of skeletal muscle.