The most common muscular diseases include muscular dystrophy, myasthenia gravis and myositis, according to MedlinePlus. Myositis is inflammation of the muscles and can be caused by injury or infection. It can also be an autoimmune condition where the body is attacked by its own immune system.
Muscular dystrophy is a gradual deterioration of the body's muscles, claims Mayo Clinic. Eventually, it makes walking and moving difficult and can result in the patient being confined to a wheelchair.
Myasthenia gravis often strikes the muscles in the face and head, says Mayo Clinic. It's a progressive disease and can result in difficulties in swallowing, speaking and breathing.