Cartilage-hair hypoplasia

Overview

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

http://rarediseases.org/rare-diseases/mckusick-type-metaphyseal-chondrodysplasia

For more information about the management of CHH, doctors can reference a recent article: Clinical Features and Management of Cartilage-Hair Hypoplasia

References
Show More Content Like This

More Overview Content

Are there other names for Cartilage-Hair Hypoplasia?

How common is Cartilage-Hair Hypoplasia?

What is the usual abbreviation for Cartilage Hair Hypoplasia?

Are there any terms that are considered derogatory when referring to Cartilage-Hair Hypoplasia?

Is Cartilage-Hair Hypoplasia more common in males or females?

Are there other names for Cartilage-Hair Hypoplasia?

When Cartilage-Hair Hypoplasia (CHH) was first discovered in the 1960's, it was called McKusick type metaphyseal chondrodysplasia, after the famous geneticist Victor McKusick who first studied this condition in the Amish population. The metaphysis is the wide part near the end of a bone. The prefix "chondro" means cartilage and dysplasia refers to abnormal growth. It has also be described as Immunodeficiency with Short-Limbed Dwarfism. Currently, CHH is the most commonly used name for this condition.

CHH is part of a group of disorders called skeletal dysplasias. Skeletal dysplasias are conditions that affect the bones of an individual and lead to short stature and shorter arms and legs. There are hundreds of different types of skeletal dysplasias and they all have different causes and different features. These types of conditions are also referred to as dwarfism, which is an older term but still used.

Cartilage-Hair Hypoplasia (CHH) is the most common name for this condition used by doctors. The other names like McKusick type metaphyseal chrondodysplasia are not used very much these days; however, these names may be referenced in older medical articles so they are still useful to know.

References
How common is Cartilage-Hair Hypoplasia?

Cartilage-Hair Hypoplasia (CHH) is a very rare disorder. There are believed to be less than 700 people currently living with CHH. Individuals have been reported in populations throughout the world, but in the Old Order Amish population between 1 in 500 to 1 in 1,000 people are thought to have CHH. That means that 1 in 10 people with Old Order Amish ancestry are carriers of a single RMRP mutation. If two carriers have a child together, there is a 25% that the child will have CHH. Carriers of a single mutation often do not know they are carriers, unless they decide to have genetic testing, because carriers of one mutation don't have any symptoms or features of the condition. People with Finnish ancestry also havea higher rate of CHH. In the Finnish population, about 1 in 23,000 people have CHH, and about 1 in 76 are carriers.

People and families living with CHH who wish to learn more about the risk to be a carrier of CHH or have an affected child should work with a genetic counselor who can give them an individual assessment. A genetic counselors in a particular area can be found on the National Society of Genetic Counselors website.

References
  • Ridanpää M, Sistonen P, Rockas S, Rimoin DL, Mäkitie O, Kaitila I. Eur J Hum Genet. 2002 Jul;10(7):439-47. Worldwide mutation spectrum in cartilage-hair hypoplasia: ancient founder origin of the major70A-->G mutation of the untranslated RMRP. http://www.ncbi.nlm.nih.gov/pubmed/12107819
  • Mäkitie, Outi and Kostjukovits, Svetlana. Cartilage-Hair Hypoplasia - Anauxetic Dysplasia Spectrum Disorders. Gene Reviews.Posting: March 15, 2012; Last Update: August 13, 2015. Accessed March 10, 2016. http://www.ncbi.nlm.nih.gov/books/NBK84550/
  • O'Neill, Marla J. F. Online Mendelian Inheritance of Man (OMIM): #250250: CARTILAGE-HAIR HYPOPLASIA; CHH - updated : 6/8/2009. Accessed March 8, 2016. http://www.omim.org/entry/250250#39
What is the usual abbreviation for Cartilage Hair Hypoplasia?

The usual abbreviation of Cartilage Hair Hypoplasia is CHH. No other common abbreviations are used by patients and doctors to describe this condition.

References
Are there any terms that are considered derogatory when referring to Cartilage-Hair Hypoplasia?

Individuals with Cartilage-Hair Hypoplasia (CHH) are part of a larger community of individuals with short stature. The oldest and largest support organization for this population is called the Little People of America (LPA). The LPA has officially come out against the use of the term "midget" to describe people with short stature, including those with CHH. This term is considered hurtful and has a history of use in abusive and bullying situations. Therefore, this term should never be used in reference to an individual with CHH or anyone else. Some people with short stature prefer the term dwarf and others prefer the term little person. Importantly, like with everyone else, individuals with CHH and other conditions of short stature are all unique individuals who may have different preferences and perspectives on such language.

References
Is Cartilage-Hair Hypoplasia more common in males or females?

Both males and females are diagnosed with Cartilage-Hair Hypoplasia (CHH) at equal rates. There is no link to gender with this condition. The gene associated with CHH, called the RMRP gene, is found on chromosome 9. Men and women all have two copies of this chromosome, so they have an equal chance of carrying a gene change on RMRP.

References

We use cookies to ensure that we give you the best experience on our website. By continuing to browse this site, you are agreeing to our use of cookies.

Continue Find out more about our use of cookies and similar technology

This content comes from a hidden element on this page.

The inline option preserves bound JavaScript events and changes, and it puts the content back where it came from when it is closed.

Remember Me