- Multifactorial inheritance (polygenic inheritance).

Multifactorial inheritance (polygenic inheritance)

 

Result from the interplay of genetic and environmental factors.

There is a similar rate of recurrence among all 1st-degree relatives (parents, siblings, offspring of the affected child). It is unusual to find a substantial increase in risk for relatives related more distantly than 2nd degree to the index case.

The magnitude of the trait is determined by number of genes (each adding a small amount to the quantity of the trait or subtracting a small from it)

Also number of environmental factors each act by adding or subtracting an amount to final result. 

Conditions often associated with multifactorial inheritance:

Congenital malformations:

•      neural tube defects

•      congenital heart disease

•      cleft lip and palate

•      pyloric stenosis

•      developmental dysplasia of the hip (DDH)

•      talipes equinovarus

•      hypospadias

Childhood:

•      atopy (especially asthma and eczema)

•      epilepsy

•      DM type 1 (insulin-dependent Diabetes).

  Adult life:

•      atherosclerosis and coronary artery disease

•      DM type 2

•      Alzheimer disease

•      malignancy (especially the common cancers, e.g. breast and colorectal cancer)

•      hypertension

•      cerebrovascular disease (especially stroke).