IGHMBP2 and proximal spinal muscular atrophy: In fact, arthrogryposis has been reported in many diseases discussed in this review article: SMARD1 due to mutations in IGHMBP2, XL-SMA due to mutations in UBA1, SP-SMA due to mutations in TVPV4, SMA-LED1 due to mutations in DYNC1H1, and SMA-LED2 due to mutations in BICD2.