Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is an autosomal recessive motor neuron disorder that affects infants. It is characterized by early breathing difficulties, generalized hypotonia, failure to thrive leading to diaphragmatic paralysis and distal limb amyotrophy. SMARD1 is caused by mutations in the IGHMBP2 gene, which encodes Ig micro-binding protein 2, located on human chromosome 11q13.2-q13.4. So far, several mutations have been described associated to SMARD1 phenotype. A splice-site mutation in mouse Ighmbp2 is responsible for spinal muscle atrophy in the neuromuscular degeneration (nmd) mouse, which serves as the animal model of SMARD1. Mice homozygous for the nmd mutation have life spans that range from 12 to 138 days and exhibit progressive and severe muscle wasting of the hind limbs, followed by the forelimbs, secondary to loss of motor neuron innervation. The cellular function of the IGHMBP2 protein is not well understood, but it seems to be involved in transcription and pre-mRNA processing. The IGHMBP2 gene is ubiquitously expressed, and the sequence of events resulting in selective motoneuron vulnerability is unknown.