What is Cartilage-Hair Hypoplasia?
Cartilage-Hair Hypoplasia (CHH) is a genetic condition that causes short stature with short arms and legs, small amounts of thin hair, an increased risk for cancer, and a weak immune system. CHH is part of a larger group of conditions called skeletal dysplasias, commonly referred to as dwarfism. Other symptoms of CHH include a lack of healthy red blood cells (anemia), and problems with the colon that can be present at birth. CHH gets its name due to poorly developed cartilage in long bones, such as the arms and legs. Cartilage is the type of tissue that helps connect our bones and hypoplasia means underdevelopment. Problems with cartilage can also cause extra flexibility in some joints, also known as hypermobility. Some people with CHH may not be able to fully extend their elbows due to problems with their cartilage. Up to 40% of people with CHH develop cancer, often before they turn 40 years old. The most common type of cancers diagnosed in people with CHH are lymphoma, a cancer of the cells in the immune system, and basal cell carcinomas which is a type of skin cancer. Other medical issues include problems with the colon (Hirschprung's disease and megacolon).
Every person with CHH does not necessarily have the same symptoms or features. There can be people who are more mildly affected and others who have more severe health problems from CHH. It is not well-understood why this is, so it is hard to predict what issues a person will have once they are diagnosed, even if they have other family members who also have the condition.
CHH is an autosomal recessive disorder meaning that in order for a person to have CHH, they have to inherit two changed copies, or two mutations, of a specific gene called RMRP. There are no treatments that prevent the main symptoms of CHH like short stature, immune issues, and anemia. However, these symptoms can be managed effectively, which is why most people with CHH have a team of doctors including experts in genetics, immunology, hematology and orthopedics.
There is a useful factsheet about CHH for people and families living with CHH at the NORD Rare Disease site
For more information about the management of CHH, doctors can reference a recent article: Clinical Features and Management of Cartilage-Hair Hypoplasia
Knutsen, Alan P. MD. Cartilage-Hair Hypoplasia. Medscape. Updated: Mar 31, 2014. Accessed March 10, 2015. http://emedicine.medscape.com/article/885807-overview
Nemour's Childrens Health Services. Skeletal Dysplasias- Cartilage Hair Hypoplasia. http://www.nemours.org/service/medical/skeletal-dysplasia/cartilagehairhypoplasia.html?tab=about
Rider, Nicholas, DO. "Cartilage-hair Hypoplasia." Cartilage-hair Hypoplasia. Up To Date, updated: Jul 10, 2014. Web. 14 Mar. 2016.http://www.uptodate.com/contents/cartilage-hair-hypoplasia#H1
Mäkitie, Outi and Kostjukovits, Svetlana. Cartilage-Hair Hypoplasia - Anauxetic Dysplasia Spectrum Disorders. Gene Reviews.Posting: March 15, 2012; Last Update: August 13, 2015. Accessed .. http://www.ncbi.nlm.nih.gov/books/NBK84550/
NORD Rare Disease site. http://rarediseases.org/rare-diseases/mckusick-type-metaphyseal-chondrodysplasia