Hereditary Spinal Muscular Malformations

There are several inherited syndromes characterized by an abnormal nerve transmission from the spinal to peripheral nerves. They manifest themselves with degeneration of the lower motor neuron in which atrophy and fasciculations are initially localized to the proximal muscles and then extend to the more peripheral ones. These abnormalities are included in spinal muscular atrophy (SMA). SMA causes progressive muscle weakness and atrophy particularly in the lower limbs and respiratory muscles. The disease is caused by specific mutations in the SMN1 gene, which codes for the survival motor neuron (SMN) protein. The number of copies of the SMN2 gene is at the basis of the great variability of the disease. The SMA type 1, Werdnig-Hoffman syndrome, is characterized by a progressive reduction in the perception of fetal movements, clubfoot, and polyhydramnios. The diagnosis is molecular.