What Your Test Results Mean:

Carriers typically show no symptoms; however, carriers are at an increased risk of having a child with CHH-AD. Risk for the current or future pregnancies is dependent on your partner’s carrier status. Carrier testing of your partner is recommended in addition to consultation with a genetic counselor.

Disease Explained:

CHH-AD spectrum disorders are inherited conditions that affect the skeletal and immune systems. The CHH-AD spectrum includes the milder cartilage-hair hypoplasia and metaphyseal dysplasia without hypotrichosis, and the more severe anauxetic dysplasia. Symptoms include short-limbed dwarfism, light-colored, sparse hair, and immune problems. Prognosis is dependent on the presence and severity of immunodeficiency. Management is focused on protecting affected individuals from infection by means of vaccinations and managing infections when they do occur. Bone marrow transplant has been used successfully to manage individuals with severe immunodeficiency.

How the Genetics Works:

CHH-AD spectrum disorders are a group of autosomal recessive disorders caused by pathogenic variants in the RMRP gene. In general, individuals have two copies of the RMRP gene. Carriers of cartilage-hair hypoplasia have a single variant in one copy of the RMRP gene while individuals with cartilage-hair hypoplasia have variants in both copies of their genes, one inherited from each parent. Risk for two carriers to have a child with the disorder is 25%.