Spinal and bulbar muscular atrophy, also known as Kennedy disease, is a genetic cause of progressive limb and bulbar weakness.

In some individuals with weakness of the proximal muscles, there may be a genetic cause.

Facioscapulohumeral muscular dystrophy is a neuromuscular condition in which genomic testing is indicated.

Myotonia is a neuromuscular condition that prevents the muscles from relaxing promptly after contraction. Nearly all cases will have a genetic cause.

Muscle cramps are common, but cramps in a young man with large calves and elevated creatine kinase levels may indicate Becker muscular dystrophy.