Werdnig-Hoffmann disease is the severe type of spinal muscular atrophy also Known as infantile SMA, and is a rare, inherited, autosomal recessive neuromuscular disease. Both parents unknowingly carry the gene for the disorder, and when the child inherits the defective gene from both parents, the disease develops.
Werdnig-Hoffmann is a disease of the anterior horn cells. These neurons, located in the spinal cord, are the main motor nerves that transmit nerve impulses from the spinal cord or brain to muscular or glandular tissue.
Molecular genetic testing has shown that all types of autosomal recessive SMA are caused by mutations in the survival motor neuron (SMN) gene on chromosome 5. Deletion of the neuronal apoptosis inhibitory protein (NAIP) gene close to the SMN gene also is associated with SMA. More patients with Werdnig-Hoffmann disease than other type of SMA have NAIP deletions. Spinal muscular atrophy destroys nerves controlling voluntary muscle movement, affecting crawling, walking, head, neck control, and swallowing