IGHMBP2 and Spinal muscular atrophy with respiratory distress type 1: Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a rare autosomal recessive neuromuscular disorder caused by mutations in the IGHMBP2 gene, which encodes immunoglobulin μ‐binding protein 2, leading to progressive spinal motor neuron degeneration.