IGHMBP2 and Spinal muscular atrophy with respiratory distress type 1: IGHMBP2 loss-of-function mutations cause the rare autosomal recessive diseases spinal muscular atrophy with respiratory distress type 1 (SMARD1) and Charcot-Marie-Tooth disease type 2S (CMT2S), which are characterized by severe neurodegeneration and myopathies (Grohmann et al, 2001; Lim et al, 2012; Cottenie et al, 2014).