In this review article, we describe SMA diseases due to the mutations of SMN1 [2], IGHMBP2 [35], GARS [36], UBA1 [37], TRPV4 [38,39,40], ASAH1 [41], DYNC1H1 [42], and BICD2 [43,44,45], but not SMA diseases due to the mutations of SCO2 [46], LAS1L [47], TRIP4 [48], ASCC1 [48], and SPTBN4 [49]. The gene discussed is TRIP4; the disease is proximal spinal muscular atrophy.