BENIGN MONOMELIC AMYOTROPHIES OF UPPER AND LOWER-LIMB ARE NOT ASSOCIATED TO DELETIONS OF SURVIVAL MOTOR-NEURON GENE

Benign monomelic amyotrophies (BMAs) are rare conditions in which neur ogenic atrophy is restricted either to the upper or lower limb. BMAs a re usually sporadic, have insidious onset and slow progression followe d by stabilization, are clinically confined for many years to a single limb and lack of sensory, bulbar, and pyramidal signs. Although the a etiology and pathogenesis of BMAs are unknown they are considered vari ants of spinal muscular atrophy with focal emphasis and a benign cours e. We studied 7 patients with BMAs to investigate whether they present alterations of the survival motor neuron gene (SMN) which has been fo und deleted or disrupted in proximal spinal muscular atrophy. All 7 pa tients showed the presence of both exon 7 and 8 of SMN gene. These fin dings indicate that deletions at the SMN locus are not present in BMA of upper and lower limb and suggest that these disorders are not only clinically but also genetically separate entities from proximal spinal muscular atrophies.