Related Experiment Videos
Multifactorial inheritance of non-syndromic macrocephaly
L Arbour1, G V Watters, J G Hall
1Department of Human Genetics, McGill University, Montreal, Quebec, Canada.
Objective:
To reevaluate previous claims that non-syndromic macrocephaly is usually inherited as an autosomal dominant trait.
Design:
Head size was measured in the parents and sibs of children with non-syndromic macrocephaly.
Outcome Measures:
If autosomal dominant inheritance is involved, the frequency distribution should be bimodal.
Results:
Head circumference of parents and sibs of the macrocephalic probands had a mean significantly greater than the population norm, and a unimodal distribution. Probands with psychomotor impairment had bigger heads, and more had a history of birth difficulty, than did unimpaired probands.
Conclusions:
The usual genetic basis for non-syndromic macrocephaly is multifactorial with a polygenic genetic basis, rather than autosomal dominant. Risk of recurrence appears to be much lower than if it would be on the assumption of autosomal dominant inheritance. Macrocephaly in a parent or sib of an unborn child may present a risk for birth injury to that child. A larger series of patients will be necessary to resolve this question.