1
Fifth stage
Pediatric
Lec-11
.د
أوس
7/3/2016
Multifactorial inheritance
Multifactorial inheritance refers to traits that are caused by a combination of
inherited and environmental factors
Characteristics
1- The risk of recurrence is related to the incidence of the disease
2- Some disorders have a sex predilection, Pyloric stenosis, for example, is more common in
males, whereas congenital dislocation of the hips is more common in females
3-The likelihood that both identical twins will be affected with the same malformation is
less than 100% but much greater than the chance that both members of a nonidentical twin
pair will be affected. This is in contrast with the pattern seen in mendelian inheritance, in
which identical twins almost always share fully penetrant genetic disorders
4- The risk of recurrence is increased when multiple family members are affected. A simple
example is that the risk of recurrence for unilateral cleft lip and palate is 4% for a couple
with 1 affected child and increases to 9% with 2 affected children
5- The risk of recurrence may be greater when the disorder is more severe. For example, an
infant who has long-segment Hirschsprung disease has a greater chance of having an
affected sibling than the infant who has short-segment Hirschsprung disease.
Conditions with multifactorial inheritance
Congenital malformations
Neural tube defects (anencephaly and spina bifida)
Congenital heart disease
Cleft lip and palate
Pyloric stenosis
Congenital dislocation of the hip
Talipes
Hypospadias
2
Adult life
Atherosclerosis and coronary heart disease
Diabetes mellitus
Asthma
Epilepsy
Hypertension