Cartilage-hair hypoplasia (CHH) primarily affects bone growth leading to short stature and various skeletal abnormalities.
CHH individuals often display fine, sparse hair and abnormal cartilage development. Some may experience a compromised immune system, making them more susceptible to infections, especially severe cases of chickenpox. Children with CHH commonly experience anemia, characterized by reduced red blood cell counts that result in fatigue and weakness, although this typically resolves by adulthood. Additionally, some CHH individuals may exhibit decreased levels of specific white blood cells. Importantly, individuals with CHH face an elevated risk of certain cancers, including non-Hodgkin’s lymphoma and skin cancer. The symptoms and their intensity can vary significantly among those affected by the condition.
CHH is caused by pathogenic (disease-causing) variants in the RMRP gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background. For example, individuals of Ashkenazi Jewish descent have a 1 in 68 chance to be a carrier.
Other names for this condition are McKusick’s metaphyseal chondrodysplasia syndrome, Metaphyseal chondrodysplasia, McKusick type, and Metaphyseal chondrodysplasia, recessive type.