Consanguinity and its relevance to clinical genetics

Consanguineous marriages have been practiced since the early existence of modern humans. Until now, consanguinity is widely practiced in several global communities with variable rates. The present study was undertaken to analyze the effect of consanguinity on different types of genetic diseases and child morbidity and mortality. Patients were grouped according to the types of genetic errors into four groups: Group I: Chromosomal and microdeletion syndromes. Group II: Single gene disorders. Group III: Multifactorial disorders. Group IV: Diseases of different etiologies. Consanguineous marriage was highly significant in 54.4% of the studied group compared to 35.3% in the control group (P < 0.05). Consanguineous marriages were represented in 31.4%, 7.1%, 0.8%, 6%, 9.1% among first cousins, one and a half cousins, double first cousins, second cousins and remote relatives respectively in the studied group. Comparison between genetic diseases with different modes of inheritance showed that recessive and multifactorial disorders had the highest values of consanguinity (78.8%, 69.8%, respectively), while chromosomal disorders had the lowest one (29.1%). Consanguineous marriage was recorded in 51.5% of our cases with autosomal dominant diseases and in 31% of cases with X linked diseases, all cases of mental retardation (100%) and in 92.6% of patients with limb anomalies (P < 0.001). Stillbirths, child deaths and recurrent abortions were significantly increased among consanguineous parents (80.6%, 80%, 67%) respectively than among non consanguineous parents. In conclusion, consanguineous marriage is significantly higher in many genetic diseases which suggests that couples may have deleterious lethal genes, inherited from common ancestor and when transmitted to their offsprings, they can lead to prenatal, neonatal, child morbidity or mortality. So public health education and genetic counseling are highly recommended in our community.