Cartilage-Hair Hypoplasia

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Cartilage-hair hypoplasia is a disorder of bone growth characterized by short stature (dwarfism) with other skeletal abnormalities; fine, sparse hair (hypotrichosis); and abnormal immune system function (immune deficiency) that can lead to recurrent infections.

Cartilage-hair hypoplasia is caused by mutations in the RMRP gene. Unlike many genes, the RMRP gene does not contain instructions for making a protein. Instead, a molecule called a noncoding RNA, a chemical cousin of DNA, is produced from the RMRP gene. This RNA attaches (binds) to several proteins, forming an enzyme complex called mitochondrial RNA-processing endoribonuclease, or RNase MRP.

Cartilage-hair hypoplasia occurs most often in the Old Order Amish population, where it affects about 1 in 1,300 newborns. In people of Finnish descent, its incidence is approximately 1 in 20,000. Outside of these populations, the condition is rare, and its specific incidence is not known. It has been reported in individuals of European and Japanese descent.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Published Date: March 01, 2015
Published By: National Institutes of Health