Cause - variety of genetic defects, each one affecting one of the filament proteins required for muscle tone and contraction

Onset - congenital to adulthood

Symptoms - weakness and poor tone in the muscles of the face, neck and upper limbs; often affects respiratory muscles; adults might experience swallowing, speech problems; scoliosis may occur

Progression - infantile-onset cases are most severe; difficulties with feeding and respiration resulting from lack of muscle strength and tone may lead to death; affected children attain motor milestones slowly, might weaken further at puberty

Inheritance - autosomal dominant, or produced by a defective gene contributed by one parent; also autosomal recessive, or produced by defective genes contributed by both parents

Facts About Myopathies