[Spinal muscular atrophy: frequent cause of congenital hypotonia in Morocco]. / L'amyotrophie spinale infantile : cause fréquente des hypotonies congénitales au Maroc.

INTRODUCTION: Congenital hypotonia is a non specific symptom frequently seen in newborns and infants, and whose etiological diagnosis is often difficult due to the lack of specialized and affordable explorations. Childhood-onset proximal spinal muscular atrophy (SMA) is an autosomal recessive disorder caused by degeneration of the anterior horn cells of the spinal cord, leading to progressive paralysis with muscular atrophy. In more than 95% of the cases, it results from deletion of exon 7 of the SMN gene localized on 5q13, easily identified by molecular biology. OBJECTIVE: To determine the prevalence of the deletion of exon 7 of the SMN gene in congenital hypotonia with an unknown cause in Morocco. PATIENTS AND METHODS: We investigated the deletion of exon 7 of the SMN gene in 87 newborns and infants with congenital hypotonia. The cause of congenital hypotonia could not be determined in 60 of them, while 27 had electrophysiological evidence for an involvement of the anterior horn cells. RESULTS: The homozygous deletion of the SMN gene was detected in 23 of the newborns with unknown cause for hypotonia (38%) and in 21 of the infants whose electromyogram suggested infantile spinal amyotrophy (78%). CONCLUSION: This study underlines the advantages of a systematic search for the deletion of exon 7 of the SMN gene in every infant suffering from congenital hypotonia due to an unknown cause, particularly when the child's vital prognosis is at stake. This genetic test, easily implemented, should be systematically proposed after an attentive clinical evaluation in countries where the etiological diagnosis of congenital hypotonia is not systematic.

Cytogenetic and epidemiological profiles of Down syndrome in a Moroccan population: a report of 852 cases.

INTRODUCTION: Trisomy 21 or Down syndrome is the most common type of autosomal chromosome abnormality, with an incidence of one out of 700 live births. Down syndrome is associated with psychomotor delay, characteristic facial features, and sometimes, cardiac, digestive and ocular malformations. The aim of this study was to estimate the proportions of various cytogenetic types of trisomy 21, and to study the link between maternal age and trisomy 21 in the Moroccan population, in order to provide data on the cytogeneticity and epidemiology of Down syndrome in Morocco. METHODS: A retrospective analysis was performed on the case records of 852 patients who were confirmed as Down syndrome by cytogenetic analysis at the Department of Medical Genetics, National Institute of Health, Morocco. RESULTS: Among the 852 cases of Down syndrome presenting over a period of 15 years, free trisomy 21 was present in 820 cases (96.24 percent). 27 patients had translocation and five cases were mosaics. The median maternal age of the Moroccan mothers at the birth of the affected child was 35.39 years. CONCLUSION: The identification of specific types of chromosomal abnormalities in Down syndrome children is important as it assists with patient management and family counselling.

Consanguineous marriages in Morocco and the consequence for the incidence of autosomal recessive disorders.

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.

A gene for non-specific X-linked mental retardation (MRX55) is located in Xp11.

A new family with a non-specific X-linked mental retardation (MRX55) is described. An X-linked recessive inheritance is suggested by the segregation from two healthy transmitting females of moderate mental retardation in three males, without any specific clinical, radiological or biological features. Two point linkage analysis demonstrated significant linkage between the disorder and several markers in Xp11 (Zmax = 2.11, theta = 0); multipoint linkage analyses confirmed the significant linkage with a maximum lod score (Z = 2.11 at theta = 0, at DXS8012). Recombination events observed with the flanking markers DXS1068 and DXS1275 delineate a 34 centimorgan interval in the pericentromeric region. The interval of assignment pointed out in this family overlaps with several MRX loci previously reported in Xp11 which are reviewed here in.