Nemaline Myopathy is characterized by muscle weakness, decreased muscle tone, and depressed or absent deep tendon reflexes. Muscle weakness is usually most severe in the face, the neck, and the proximal limb muscles. There are several different forms of the disease, with some being more severe than others. In the more severe forms, respiratory distress and feeding and swallowing difficulties are common and can lead to early death.

There are six different genes in which mutations have been found to cause Nemaline Myopathy. A single mutation in the Nebulin gene, located on chromosome 2, has a carrier frequency of 1 in 108 in the Ashkenazi Jewish population. Affected individuals with mutations in the Nebulin gene often have a milder form of the disease, although rarely, they can be more severely affected.