Consanguineous Marriages in Morocco and the Consequence for the Incidence of Autosomal Recessive Disorders

Abstract

Consanguineous marriage is traditionally common throughout Arab countries. This leads to an increased birth prevalence of infants with recessive disorders, congenital malformations, morbidity and mortality. The aim of this study was to evaluate the rate of consanguineous marriage in families with autosomal recessive diseases, and to compare it with the average rate of consanguinity in the Moroccan population. The study was conducted in the Department of Medical Genetics in Rabat on 176 families with autosomal recessive diseases diagnosed and confirmed by clinical, radiological, enzymatic or molecular investigations. The rate of consanguinity was also studied in 852 families who had infants with trisomy 21 confirmed by karyotyping. These families were chosen because: (i) there is no association between trisomy 21 and consanguinity, (ii) these cases are referred from different regions of Morocco and (iii) they concern all social statuses. Among 176 families with autosomal recessive disorders, consanguineous marriages comprised 59.09% of all marriages. The prevalence of consanguinity in Morocco was found to be 15.25% with a mean inbreeding coefficient of 0.0065. The differences in the rates of consanguineous marriages were highly significant when comparing the general population and couples with offspring affected by autosomal recessive conditions. These results place Morocco among the countries in the world with high rates of consanguinity. Autosomal recessive disorders are strongly associated with consanguinity. This study better defines the health risks associated with consanguinity for the development of genetic educational guidelines targeted at the public and the health sector.

The Moroccan Genetic Disease Database (MGDD): a database for DNA variations related to inherited disorders and disease susceptibility

“…In a previous study, the rate of consanguineous marriages in Morocoo was shown to correlate with the high prevalence of autosomal recessive disorders. 9 This is similar to the situation in Tunisia, where frequencies of autosomal recessive and dominant disorders were 62.9% and 22.9%, respectively. 17 The disease classification reveals that endocrine, nutritional and metabolic diseases, congenital malformations and neurodegenerative diseases are the major categories of Mendelian disorders in the Moroccan population, with similar prevalence as in the Tunisian population.…”

“…8 A recent study estimates the frequency of consanguineous marriages to be 59.09% among families with autosomal recessive disorders. 9 Despite the improvement in the health-care system in Morocco, few epidemiological data are available about the prevalence of genetic diseases. Cancer is a major health problem and a common cause of death.…”

Consanguinity, endogamy, and genetic disorders in Tunisia

“…Moreover, our findings seem to confirm those found in other nearby populations. Indeed, a similar recent study conducted in Morocco among 176 patients with autosomal recessive diseases showed that these disorders are strongly associated with consanguinity (Jaouad et al 2009). Likewise, a previous study conducted on a cohort of 100 Egyptian patients suffering from various recessive autosomal conditions reported that the frequency of consanguinity among parents of patients was significantly higher (p < 0.01) than that reported for the general Egyptian population (Mokhtar et al 1998).…”

“…However, deleterious autosomal recessive alleles are sometimes hidden within the family in the heterozygous state for many generations, and consanguineous unions between mutation carriers will lead them to come to the surface. This effect is more remarkable for rare diseases since there is little probability that the carrier finds a partner who bears the same mutation in the general population (Jaouad et al 2009). A previous study on the effects of parental consanguinity on genetic disorders in the Iranian population has reported that consanguineous couples who already have an affected child are 13 times more likely to have another affected sibling (Mokhtari and Amrita 2003).…”

“…Many reports have highlighted a positive association between inbreeding and a number of recessive single gene disorders like achromatopsia (Tchen et al 1977), Leber's congenital amaurosis, xeroderma pigmentosum (Mokhtar et al 1998), and metabolic defects like aminoacidopathies and mucopolysaccharidoses (Jaouad et al 2009). However, some authors believe that a long practice of inbreeding over several generations leads to the elimination of deleterious recessive mutations from the population gene pool (Khoury et al 1987).…”