Achondroplasia
| Achondroplasia | |
|---|---|
 |
|
| Jason "Wee Man" Acuña actor with achondroplasia | |
| Pronunciation | /eɪˌkɒndrəˈpleɪziə, ə-, -ˈpleɪʒiə, -ˈpleɪʒə/ |
| Classification and external resources | |
| Specialty | Medical genetics |
| ICD-10 | Q77.4 |
| ICD-9-CM | 756.4 |
| OMIM | 100800 134934 |
| DiseasesDB | 80 |
| MedlinePlus | 001577 |
| eMedicine | article/1258401-overview |
| Patient UK | Achondroplasia |
| MeSH | D000130 |
Achondroplasia is a common cause of dwarfism. It occurs as a sporadic mutation in approximately 80% of cases (associated with advanced paternal age) or it may be inherited as an autosomal dominant genetic disorder.
People with achondroplasia have short stature, with an average adult height of 131 centimeters (52 inches) for males and 123 centimeters (48 inches) for females. Achondroplastic adults are known to be as short as 62.8 cm (24.7 in). If both parents of a child have achondroplasia, and both parents pass on the mutant gene, then it is very unlikely that the homozygous child will live past a few months of its life. The prevalence is approximately 1 in 25,000.
Achondroplasia is caused by a mutation in fibroblast growth factor receptor 3 (FGFR3). In normal development FGFR3 has a negative regulatory effect on bone growth. In achondroplasia, the mutated form of the receptor is constitutively active and this leads to severely shortened bones. The effect is genetically dominant, with one mutant copy of the FGFR3 gene being sufficient to cause achondroplasia, while two copies of the mutant gene are invariably fatal (recessive lethal) before or shortly after birth (known as a lethal allele). A person with achondroplasia thus has a 50% chance of passing dwarfism to each of their offspring. People with achondroplasia can be born to parents that do not have the condition due to spontaneous mutation.
New gene mutations leading to achondroplasia are associated with a father older than the age of 35. Studies have demonstrated that new gene mutations for achondroplasia are exclusively inherited from the father and occur during spermatogenesis; it is theorized that oogenesis has some regulatory mechanism that prevents the mutation occurring in females.
There are two other syndromes with a genetic basis similar to achondroplasia: hypochondroplasia and thanatophoric dysplasia.
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Wikipedia