Cartilage-hair hypoplasia

Cartilage-hair hypoplasia (English Cartilage-Hair Hypoplasia) is a form of disproportionate short stature . It is caused by a genetic change that affects the growth of long bones as well as various other disorders such as reduced hair growth or a vulnerable immune system. Since the phenotype can vary widely, cartilage-hair hypoplasia (CHH), anauxetic dysplasia (AD), and metaphyseal dysplasia without hypotrichosis (MDWH) are summarized as cartilage-hair hypoplasia-anauxetic dysplasia spectrum disorder. Another common name is McKusick Type Metaphyseal Chondrodysplasia. The disease was first described in an Amish population by Victor Almon McKusick .

Symptoms

Due to the very different manifestations, only the short stature is a certain symptom. For the lighter forms CHH and MDWH, a range of 103 cm to 149 cm is given in the literature. The size range is thus comparable to that of achondroplasia / hypochondroplasia , although the disproportionality in cartilage-hair hypoplasia is not so important.

Cartilage-Hair Hypoplasia (CHH)

• mild to severe disproportionate short stature (100%), occurrence prenatal in 76–93%
• short fingers and toes
• very fine, blonde hair (89–93%)
• varus deformed limbs (77%)
• slack ligaments with hypermobility of the joints (in 87%)
• limited movement of the elbows (83%)
• Immunodeficiency (88%)
• Anemia (79%) that disappears during childhood

Metaphyseal dysplasia without hypotrichosis (MDWH)

• symptoms similar to cartilage-hair hypoplasia, but with normal hair growth
• No immunodeficiency or anemia

Anauxetic dysplasia (AD)

• prenatal occurrence of extremely disproportionate short stature (100%)
• Bell chest with hyperlordosis and kyphosis
• Hip malposition
• Cervical vertebrae - subluxation which leads to compression of the cervical spine
• small face and macroglossia
• abnormal tooth growth
• low intellectual disability

root cause

The cause of the symptoms is a mutation in the RMRP gene. Inheritance is autosomal recessive. Both alleles must have a disorder for symptoms to appear. In the case of a new mutation (families without previously reported cases), both alleles usually have a different mutation ( complex heterozygosity ).

frequency

Due to the recessive inheritance, the cartilage-hair hypoplasia is particularly common in certain isolated communities. In the old order Amish there is an incidence of 1–2: 1000, in Finland 1 : 23,000. This makes cartilage-hair hypoplasia one of the most common forms of short stature in Finland. In other nations, case numbers are reported in the lower double-digit range, which corresponds to a frequency of less than 1: 1,000,000.

Web links

• Cartilage-hair hypoplasia.  In: Online Mendelian Inheritance in Man . (English)

Individual evidence

1. ↑ CARTILAGE-HAIR HYPOPLASIA; CHH omim.org. Retrieved March 24, 2020
2. ↑ Mäkitie O, S .: Vakkilainen Cartilage-Hair Hypoplasia - Anauxetic dysplasia Spectrum Disorders. March 15, 2012 (Updated May 24, 2018). In: Adam MP, Ardinger HH, Pagon RA, et al., Editors. GeneReviews® (Internet).
3. ↑ Outi Mäkitie, Jaakko Perheentupa, Ilkka & Kaitila: Growth in Cartilage-Hair Hypoplasia. Pediatric Research 31, 176-180 (1992). ( [1] )
4. ↑ LYHYTKASVUISUUDESTA. Lyhytkasvuiset - Kortväxta ry, accessed April 10, 2020 (Finnish). 
5. ↑ Outi Mäkitie, Tuija Sulisalo, Albert de la Chapelle, Ilkka Kaitila: Cartilage-hair hypoplasia. Journal of medical genetics 32, 39-43 (1995). ( [2] )

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !