Genetic effects of consanguineous marriages

Consanguineous marriages - It is a marriage of biologically (blood) related persons, they can be 1^st degree, 2^nd degree or 3 degree cousins. 
Advantages:

• Early marriage
• More stable marriage
• More children
• More convenient for parents
• More or less equivalent socioeconomic and cultural background in the couple

Genetic effects - As both parents share more or less similar genetic information, there is increased risk for transmission of autosomal recessive diseases. Of course 1^st degree cousins have more empirical risks than 2^nd or 3^rd degree cousins.

What is an autosomal recessive (AR) disease?

It is a genetic inherited disease transmitted from two completely healthy parents, each of them carrier of a defect in one copy of his gene. When both abnormal gene copies are transmitted to the offspring, the disease starts to appear.
The risk of this couple to have an affected child is 25% or ¼ and it is the same risk for each pregnancy.
Examples of these diseases are thalassemia, sickle cell anemia, most of metabolic diseases, some mental retardation, some neurological or neuromuscular diseases, familial Mediterranean fever, and cystic fibrosis.

How to avoid appearance of autosomal recessive DISEASES in my family?

Genetic screening whether premarital or preconception to detect the carrier status of the parents and to avoid conception of an affected offspring by genetic analysis.

However, if pregnancy occurs, we can also do early prenatal diagnosis as early as 12 weeks of gestation but the genetic status of the parents should be determined early before 12 weeks of gestation to allow prenatal or pre-conception diagnosis. 

How to know that we have an autosomal recessive disease in my family?

By recurrence of the same clinical manifestations in more than one offspring derived from consanguineous parents. However, you should not wait for that to do genetic screening for your couple if you are consanguineous parents.
To be noted that consanguineous marriage is common in North Africa, East Asia, and middle east.

Dr. Azza Abd El Moneim Attia Mohamed
French Board
Consultant Clinical Genetics