Achondroplasia is an uncommon condition, and its recurrence risk depends on whether one or both of the parents has the disease.
Inheritance: autosomal dominant with high (100%) penetrance
Frequency: 1 in 15,000 to 1 in 40,000 live births
Parental status patterns:
(1) neither parent has clinical achondroplasia
(2) one parent normal, one parent with achondroplasia
(3) both parents with achondroplasia
neither parent with achondroplasia (both normal)
0.02% with achondroplasia
one parent with achondroplasia, second normal
50% heterozygous for achondroplasia,
both parents with achondroplasia
50% heterozygous for achondroplasia
• The risk of recurrence in "sporadic" cases with phenotypically normal parents depends on the mutation rate and the occurrence of gonadal mosaicism (Mettler and Fraser). Because of gonadal mosaicism, the recurrence rate should be higher than twice that of the mutation rate (a rate of 1 in 20,000 would be 0.005%; 2 times this 0.01%).
• The risk of recurrence of "sporadic" cases appears related to a paternal age > 35 years of age.
• Homozygous achondroplasia is lethal as a neonate.
To read more or access our algorithms and calculators, please log in or register.