Wednesday, 8 August 2007

MRCOG Achondroplasia

Achondroplasia

This is the most common non lethal skeletal dysplasia.
The clinical characteristics are: short stature (proximal shortening of limbs), large head, and hypoplastic mid face.

Large head with frontal bossing is a common feature but hydrocephalus can also occur(1)

I.Q is usually normal.(2)

Mode of inheritance is autosomal dominant.

Prenatal testing
(a) High risk pregnancy-This is where one or both parents having achondroplasia. It can be done by analysing the cells from chorionic villus sampling or amniocentesis. The objective is identify the fatal homozygous (both genes are defective) achondroplasia from heterozygous (one gene is defective).

(b) Low risk pregnancy: ultrasound done at 22 weeks may detect short foetal limbs.(3)

The children with achondroplasia can also have normal limb lengths at birth

Achondroplasia is also associated with polyhydramnios.(4)