All of the myopathies are associated with muscle weakness and lack of muscle tone (dystonia). Nemaline myopathy is differentiated from other myopathies by the presence of rod-shaped inclusion bodies or nemaline rods in the skeletal muscles; there is also a higher than normal preponderance of slow muscle tissue. Nemaline myopathy is evident from birth or infancy and therefore is considered to be congenital. Large muscles groups (e.g., thighs) may be very weak or thin; due to the lack of muscle tone these infants may be described as “floppy” .
Congenital non-progressive weakness, especially of the proximal muscles. The muscles are thin and resemble rods.