A rare syndrome characterized by lower motor neuron disease associated with progressive myoclonic epilepsy, referred to as "spinal muscular atrophy associated with progressive myoclonic epilepsy" (SMA-PME), has been described in childhood and is inherited as an autosomal recessive trait.
We consider that this case represents a previously unrecognized type of lower motor neuron disease that resulted from homozygous deletion of the SMN2 gene.
A rare variant with associated myoclonic epilepsy and lower motor neuron disease had been previously described in three families before the SMN gene, responsible for the common form of SMA, was isolated.
Homozygous SMN1 (survival motor neuron) gene deletion causes spinal muscular atrophy, and SMN2 gene deletions are possible risk factors in lower motor neuron disease.