The recent identification of mutations in POP1 (Processing of precursor 1) [MIM 602486], which encodes a protein component of the nuclear ribonucleoprotein complex in two siblings with anauxetic dysplasia [33] may support the involvement of the nuclear ribonucleoprotein complex rather than the mitochondrial complex in the etiology of these severe skeletal dysplasias. The gene discussed is POP1; the disease is skeletal dysplasia.