that is transcribed by RNAse MRP. Metaphyseal dysplasia without hypotrichosis Metaphyseal dysplasia Without Hypotrichosis (MDWH) patients are unable to produce normal, new tubular structures in the metaphyses of long bones. People diagnosed with MDWH will therefore tend to experience porous and expanded long bones. The mutation occurs on the RMRP gene in MDWH; the common insertion being (-21-20 insTCTGTGAAGCTGGGGAC) on the paternal allele and a 218A→G point mutation occurring on the maternal allele. MDWH is most likely a variant of CHH. They are the same in that they both display short stature. Some of the same genes involved in the mutations in CHH are the same genes that are mutated in MDWH. These two diseases do differ in that MDWH lacks immunodeficiency and other skeletal features found in CHH patients. Anauxetic dysplasia AD is an autosomal recessive spondylometaepiphyseal dysplasia typically characterized by an early (prenatal) onset of extremely short stature and adults that do not typically exceed 85 cm in height. A less than normal amount of teeth and slight mental retardation are also typical of AD. The associated mutation(s) are a homozygous insertion mutation and two compound heterozygous mutations. Mutations in the promoter 5' regulatory region have been associated with this severe skeletal disease. Other names used to describe this condition are spondylometaepiphyseal dysplasia, anauxetic type, spondylometaepiphyseal dysplasia, Menger type. Kyphomelic dysplasia KD is a form of short-limbed dwarfism. Characteristics of KD are bowing of long bones, dysmorphia, flattened vertebrae, and short ribs. Femoral bowing is the hallmark diagnostic characteristic of KD. Novel mutations have been discovered in the RMRP gene of a single patient with KD, specifically, a mutation (insertion) of T at 194-195 paternal allele and a 63C-->T point mutation of the maternal allele. As with OS, the MSRP gene has not been strictly linked to the diseases but current research is suggestive that the MSRP gene is a factor. KD has been observed in very few patients yet this sublethal disease remains relevant to discussions of the distinct manifestations of minimal change disease. KD is rather similar to several forms of MCD in that it exhibits combined immune deficiency and aplastic anemia. Omenn syndrome Omenn syndrome (OS) is a severe immunodeficiency disease, mostly characterized by scaly erythroderma and severe reddening of the skin. OS is also commonly accompanied by enlarged lymphoid tissues, protracted diarrhea, failure to thrive, and eosinophilia. Gene sequences of people with OS reveal