Spinal muscular atrophy

Since the 1890s when Guido Werdnig and Johann Hoffmann presented a complete picture of spinal muscular atrophy (SMA), clinicians have been aware of the serious nature of this floppy infant syndrome which often occurs in siblings with normal parents. Patients experience onset during the first year of life, progressive floppiness and weakness and death from pneumonia in early childhood. In order to accommodate some clinical heterogeneity, a classification system was devised by an international group as follows: SMA type 1 (or I) for onset of symptoms before age 6 months, SMA type 2 (II) for onset between 6 and 18 months, and SMA type 3 (III) for onset after age 18 months. Gilliam et al established linkage of autosomal recessive SMA to chromosome 5q11.2-13.3 in 1990. The survival motor neuron gene (SMN), at 5q13, was found to contain deletions in > 98% SMA patients. Management consists of preventing or treating the complications of severe weakness, such as restrictive lung disease, poor nutrition, orthopedic deformities, immobility, and psychosocial problems.