Chondrodysplasia punctata (CDP) is an uncommon but well-known skeletal abnormality characterized by irregular punctate calcification of dystrophic epiphyseal cartilage and certain other cartilaginous structures, such as the larynx. The most common forms of CDP include rhizomelic CDP (“RCDP”)[Gilbert et al., 1976; Heymans et al., 1985]; X-linked dominant CDP (“CDPX2”)[Happle, 1979]; X-linked recessive CDP (CDPX1)[Maroteaux, 1989]; and autosomal dominant Conradi-Hünermann syndrome [Silengo et al., 1980]. Common associated abnormalities include prenatal and postnatal growth retardation, rhizomelic or rhizomesomelic limb shortness, ichthyosis, cataracts, and mental retardation [Happle, 1981; Spranger et al., 1971]. Although classical RCDP has been known since 1985 to be caused by several different abnormalities of plasmalogen biosynthesis [Heymans et al., 1985], and X-linked recessive CDP was recently shown to be caused by a deficiency of arylsulfatase E [Daniele et al., 1998; Franco et al., 1995], the biochemical nature of other forms of CDP remains unknown. An important metabolic disorder in which patients have rhizomesomelic limb shortness and, occasionally, calcific epiphyseal stippling [Gemme et al., 1978; Mei-