Achondroplasia (OMIM100800) is caused by heterozygous mutations in the gene that encodes fibroblast growth factor receptor 354, rhizomelic chondrodysplasia punctata type1 (RCDP1) (OMIM 215100) is caused by homozygous or compound heterozygous mutations in the gene that encodes peroxisomal biogenesis factor 7 (PEX7)55, and spondyloepiphyseal dysplasia congenital (OMIM183900) is caused by heterozygous mutations in COL2A156. The gene discussed is PEX7; the disease is achondroplasia.