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Cartilage–hair hypoplasia (CHH), also known as McKusick type metaphyseal chondrodysplasia,:578 is a rare genetic disorder. Symptoms may include short-limbed dwarfism due to skeletal dysplasia, variable level of immunodeficiency, and predisposition to cancer. It was first reported in 1965 by McKusick.
|Synonyms||McKusick type metaphyseal chondrodysplasia|
|Cartilage-hair hypoplasia has an autosomal recessive pattern of inheritance|
Short limb dwarfism|
Very fine thin light hairs and eyebrows
Hyperextensible joints of hand and feet
Abnormalities of spine
Defective antibody and cell mediated immunity
Signs and symptomsEdit
- Short limb dwarfism
- very fine thin light hairs and eyebrows
- hyperextensible joints of hand and feet
- abnormalities of spine
- defective antibody and cell mediated immunity
CHH is an autosomal recessive inherited disorder. It is a highly pleiotropic disorder. A rarely encountered genetic phenomenon, known as uniparental disomy (a genetic circumstance where a child inherits two copies of a chromosome from one parent, as opposed to one copy from each parent) has also been observed with the disorder.
An association between mutations near or within the ncRNA component of RNase MRP, RMRP, has been identified. The endoribonuclease RNase MRP is a complex of RNA molecule and several proteins and it participates in cleavage of mitochondrial primers responsible for DNA replication and in pre-rRNA processing in the nucleolus. The locus of the gene has been mapped to the short arm of chromosome 9.
Patients with CHH usually suffer from cellular immunodeficiency. In the study of 108 Finnish patients with CHH, there was detected mild to moderate form of lymphopenia, decreased delayed type of hypersensitivity and impaired responses to phytohaemagglutinin. This leads to susceptibility to and, in some more severe cases, mortality from infections early in childhood. There has also been detected combined immunodeficiency in some patients  Patients with CHH often have increased predispositions to malignancies.
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A verified treatment for this disease is yet to be discovered. Over the years, a number of treatments have been claimed to have been discovered in the east. Chinese medicines have claimed to be able to cure dwarfism for many years, but as of yet, not one verified case has been demonstrated of someone who is a dwarf or suffering from any other similar disability growing to a "normal" height.
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