RNU12-2P and proximal spinal muscular atrophy: RNAseq analyses indicated increased U12-type intron retention along with U12 small nuclear ribonucleoprotein upregulation.32 There is mounting evidence suggesting that the minor spliceosome contributes to the pathophysiology underlying neurodegenerative disorders such as spinal muscular atrophy.33,34 Taking into account that patients with pathogenic variants in RNPC3 from four different pedigrees had similar neurological findings, we speculate that splicing defects in some U12-type introns in neurons may contribute to this phenotype in our patients.