Heterogeneity in spinal muscular atrophy with respiratory distress type 1.

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a clinically heterogeneous disorder linked to mutations in the immunoglobulin mu-binding protein 2 (IGHMBP2) gene on chromosome 11q13-q21. Most infants with SMARD1 present between six weeks and six months of age with respiratory distress secondary to diaphragmatic weakness and progressive distal weakness. Sensory and autonomic dysfunctions sometimes accompany the motor weakness. This report describes a male infant with genetically confirmed SMARD1 presenting with onset of disease in the first two weeks of life with respiratory compromise and urinary retention, which has not been reported before and adds to the phenotypic variability of SMARD 1.