Cartilage-Hair Hypoplasia (CHH)
Description
Cartilage-Hair Hypoplasia (CHH) is a rare genetic disorder that primarily affects bone growth and hair development. This condition leads to short stature, distinctive hair characteristics, and other health concerns. Understanding CHH is crucial for proper diagnosis, management, and supporting individuals living with this condition.
Genes Involved
Genes Involved in Cartilage-Hair Hypoplasia (CHH)
The primary gene responsible for CHH is called RMRP. Mutations in this gene disrupt the production of a vital RNA molecule, leading to the disorder. There are other genes that, when mutated, can contribute to CHH or related conditions, including:
- RMRP: The most common gene linked to CHH. Mutations in this gene cause the classic form of the disorder.
- NUDT16: This gene plays a role in cellular processes, and its mutations are associated with a milder form of CHH.
- NOP56: Mutations in this gene may result in a rare, severe form of CHH.
- TCOF1: This gene, when mutated, can cause Treacher Collins syndrome, which shares some features with CHH.
Recognizing the Signs and Symptoms
Recognizing the Signs and Symptoms of Cartilage-Hair Hypoplasia (CHH) can be challenging, as the severity of symptoms varies significantly. However, common signs include:
- Short stature: Individuals with CHH are typically much shorter than average, with a disproportionate short trunk.
- Hair abnormalities: Hair is often thin, sparse, and brittle, sometimes with a characteristic ‘peach fuzz‘ appearance. Hair loss can also be a feature.
- Skeletal abnormalities: Besides short stature, CHH can cause other bone abnormalities, such as bowed legs, club feet, and joint problems.
- Delayed bone development: The bones may develop slower than normal, leading to delayed motor milestones.
- Immune system issues: People with CHH are more susceptible to infections, especially respiratory infections.
- Other potential complications: CHH may be associated with issues in the gastrointestinal tract, kidneys, and nervous system, but these are less common.
Causes
Causes of Cartilage-Hair Hypoplasia (CHH)
Cartilage-Hair Hypoplasia is an inherited condition. It is caused by genetic mutations, primarily in the RMRP gene. These mutations disrupt the function of the RNA molecule, leading to the characteristic symptoms of the disorder.
Inheritance/recurrence risk
Inheritance or Recurrence Risk of Cartilage-Hair Hypoplasia (CHH)
CHH is typically inherited in an autosomal recessive pattern. This means that both parents must carry a copy of the mutated gene to have a child with the disorder. If both parents are carriers, there is a 25% chance with each pregnancy that their child will inherit CHH. If one parent has the condition, their children have a 50% chance of inheriting it.
