Spinal muscular atrophy.

Proximal childhood spinal muscular atrophy is a common autosomal recessive disorder that results in degeneration of lower motor neurons of the spinal cord. The defective gene, survival of motor neuron, encodes a novel protein with a putative role in RNA metabolism. Further work is required to define clearly the mechanism by which the survival of motor neuron gene defect would result in motor neuron degeneration.