Cartilage–hair hypoplasia explained

Cartilage-hair hypoplasia
Symptoms:	Short limb dwarfism Very fine thin light hairs and eyebrows Hyperextensible joints of hand and feet Abnormalities of spine Neutropenia Defective antibody and cell mediated immunity
Synonyms:	McKusick type metaphyseal chondrodysplasia^[1]

Cartilage–hair hypoplasia (CHH) 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 by Victor McKusick in 1965.

Signs and symptoms

• Short limb dwarfism
• Very fine, light hairs and eyebrows
• Hyperextensible joints of hand and feet
• Abnormalities of spine
• Neutropenia
• Defective antibody and cell mediated immunity

Genetics

CHH is an autosomal recessive^[2] 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.^{[3] [4] [5] [6]} 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.^{[7] [8]} The locus of the gene has been mapped to the short arm of chromosome 9.^[9]

Immunodeficiency

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 phytohemagglutinin.^[10] 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.^[11] Patients with CHH often have increased predispositions to malignancies.

Treatment

A verified treatment for this disease is yet to be discovered.

See also

• List of cutaneous conditions
• List of radiographic findings associated with cutaneous conditions

Further reading

• Mäkitie. Outi. Kostjukovits. Svetlana. Cartilage-Hair Hypoplasia – Anauxetic Dysplasia Spectrum Disorders. GeneReviews. 22420014. 1 January 1993. 5 May 2017. University of Washington, Seattle.

Notes and References

1. James, William; Berger, Timothy; Elston, Dirk (2005). Andrews' Diseases of the Skin: Clinical Dermatology(10th ed.). Saunders. .
2. Sulisalo T, Makitie O, Sistonen P, Ridanpaa M, el Rifai W, Ruuskanen O, de la Chapelle A, Kaitila L . Uniparental disomy in cartilage-hair hypoplasia . European Journal of Human Genetics . 5 . 1 . 35–42 . 1997 . 10.1159/000484729 . 9156319 .
3. Bonafé L, Schmitt K, Eich G, Giedion A, Superti-Furga A . RMRP gene sequence analysis confirms a cartilage-hair hypoplasia variant with only skeletal manifestations and reveals a high density of single-nucleotide polymorphisms . Clinical Genetics. 61 . 2 . 146–51 . February 2002 . 11940090 . 10.1034/j.1399-0004.2002.610210.x. 7284120 .
4. Ridanpää M, van Eenennaam H, Pelin K, Chadwick R, Johnson C, Yuan B, vanVenrooij W, Pruijn G, Salmela R, Rockas S, Mäkitie O, Kaitila I, de la Chapelle A . Mutations in the RNA component of RNase MRP cause a pleiotropic human disease, cartilage-hair hypoplasia . Cell . 104 . 2 . 195–203 . 2001 . 11207361 . 10.1016/S0092-8674(01)00205-7. 13977736 . free . 2066/185709 . free .
5. Martin AN, Li Y . RNase MRP RNA and human genetic diseases . Cell Research. 17 . 3 . 219–26 . 2007 . 17189938 . 10.1038/sj.cr.7310120. free .
6. Kavadas FD, Giliani S, Gu Y, Mazzolari E, Bates A, Pegoiani E, Roifman CM, Notarangelo LD . Variability of clinical and laboratory features among patients with ribonuclease mitochondrial RNA processing endoribonuclease gene mutations . The Journal of Allergy and Clinical Immunology . 122 . 6 . 1178–84 . 2008 . 18804272 . 10.1016/j.jaci.2008.07.036. free .
7. 2328993. 540–544. 1990. Hsieh. C. L.. The gene for the RNA component of the mitochondrial RNA-processing endoribonuclease is located on human chromosome 9p and on mouse chromosome 4. Genomics. 6. 3. Donlon. T. A.. Darras. B. T.. Chang. D. D.. Topper. J. N.. Clayton. D. A.. Francke. U. 10.1016/0888-7543(90)90483-b.
8. 330329. 793–799. 1990. Topper. J. N.. Characterization of human MRP/Th RNA and its nuclear gene: Full length MRP/Th RNA is an active endoribonuclease when assembled as an RNP. Nucleic Acids Research. 18. 4. Clayton. D. A.. 1690392. 10.1093/nar/18.4.793.
9. 7981754. 338–341. 1993. Sulisalo. T. Cartilage-hair hypoplasia gene assigned to chromosome 9 by linkage analysis. Nature Genetics. 3. 4. Sistonen. P. Hästbacka. J. Wadelius. C. Mäkitie. O. de la Chapelle. A. Kaitila. I. 10.1038/ng0493-338. 7752268.
10. 8444246. 211–7. 1993. Mäkitie. O. Cartilage-hair hypoplasia--clinical manifestations in 108 Finnish patients. European Journal of Pediatrics. 152. 3. Kaitila. I. 10.1007/bf01956147. 10611620.
11. 165279. 868–72. 1975. Saulsbury. F. T.. Combined immunodeficiency and vaccine-related poliomyelitis in a child with cartilage-hair hypoplasia. The Journal of Pediatrics. 86. 6. Winkelstein. J. A.. Davis. L. E.. Hsu. S. H.. d'Souza. B. J.. Gutcher. G. R.. Butler. I. J.. 10.1016/s0022-3476(75)80216-2.