osomal recessive defect.. Achondroplasia
- cell-signaling defect in fibroblast growth factor receptor 3 (FGFr3).
- Dwarfism: short limbs but head/trunk normal.
- A/W advanced paternal age
Achondroplasia is associated with a mutation in the gene for:
- Fibroblast growth factor
- Platelet activating factor
- Achondroplasia is a common nonlethal form of chondrodysplasia. It is transmitted as an autosomal dominant trait with complete penetrance. De novo mutations cause 75-80% of cases. The mutation rate is estimated to be 0.000014 per gamete per generation.
- Cardinal features include short stature, rhizomelic shortening of the arms and legs, a disproportionately long trunk, trident hands, midfacial hypoplasia, prominent forehead (frontal bossing), thoracolumbar gibbus, true megalencephaly, and caudal narrowing of the interpedicular spaces.
- Achondroplasia is caused by mutations in the gene for fibroblast growth factor receptor-3 (FGFR3).
The chances of having an unaffected baby, when both parents have achondroplasia, are:
Correct answer : B. 25%
Achondroplasia is autosomal dominant.
Features of Achondroplasia are
b.Rhizomelic shortening of limbs
d.Tombstone iliac bones
a) Achondroplasia is the most common type of short limb skeletal dysplasia which shortens stature
b) Achondroplasia is an aut
- c) The short pedicles of achondroplasia lead to spinal stenosis and paraplegia more than 15% of patients
- d) Hydrocephalus is an uncommon complication in patients with achondroplasia
- e) About 90% of the cases of achondroplasia occur from a spontaneous mutation in patients with normal parents
- a, c, e
Achondroplasia is the most common type of short limb skeletal dysplasia which shortens stature. It is an autosomal dominant defect in endochondral bone formation (osteochondrodysplasia) which causes skeletal growth derived from cartilage to be shortened. The most significant shortening occurs in long tubular bones, cranial base, and spinal pedicles. The short pedicles of achondroplasia lead to spinal stenosis and paraplegia more than 15% of patients. Hydrocephalus is a concern in 60% of patients with achondroplasia. About 90% of the cases of achondroplasia occur from a spontaneous mutation in patients with normal parents. However, it’s mode of inheritance is autosomal dominant.