SMN1 and proximal spinal muscular atrophy: Spinal muscular atrophy (SMA) is the most common genetic cause of infant death worldwide and yet is generally considered to be a relatively obscure condition.18 It is an autosomal recessive disorder caused by deletions of the Survival Motor Neuron (SMN) gene.19, 20 SMN deletions trigger in the apoptotic loss of the alpha motor neurones of the spinal cord, result in progressive and symmetrical atrophy of the voluntary muscles of the limbs and trunk.