Genetic heterogeneity in spondylo-epimetaphyseal dysplasias: a clinical and radiological study

Introduction: Spondylo-epi-metaphyseal dysplasias (SEMD) are a heterogeneous group of skeletal disorders characterized by defective growth and modeling of the spine and long bones. Different types are described in the literature. Accurate classification of SEMDs is essential for proper genetic counseling. Patients and Methods: This study included 20 cases of SEMDs diagnosed by clinical and radiological findings. Cases were classified based on additional associated clinical and/or radiological features into 7 subtypes. Different subtypes were discussed with review of the literature. Results: The study illustrated the heterogeneity of SEMDs and emphasized the importance of detailed and meticulous clinical genetic and biochemical evaluation in addition to comprehensive radiological investigations for such group of disorders. It also recommends further molecular studies to identify the molecular bases of the different types. Keywords: Spondyloepimetaphyseal dysplasias, Genetic heterogeneity, Dyggve- Melchior-Clausen dysplasia, Glycoaminoglycans. Egypt. J. Hum. Genet Vol. 8 (2) 2007: pp. 147-17

Clinical, anthropometric, radiological and molecular characteristics of Egyptian achondroplasia patients

Background: Achondroplasia is the most common form of non lethal skeletal dysplasia. It is a fully penetrant autosomal dominant disorder and the majority of cases are sporadic resulting from de novo mutations associated with advanced paternal age. The phenotype of achondroplasia is related to disturbance in endochondral bone formation due to mutations in the fi broblast growth factor receptor-3 (FGFR3) gene. Aim of the Work: Evaluation of the cardinal phenotypic features in achondroplasia, the body physique using anthropometric measurements, the characteristic radiological signs in the patients as a main tool for diagnosis and detection of the most common mutations in achondroplasia patients in the studied sample.Subjects and Methods: From 42 cases referred to us as achondroplasia, we selected 20 cases where clinical manifestations were consistent with achondroplasia. Cases were subjected to full clinical examination, detailed anthropometric measurements, whole body skeletal survey and molecular studies of the most common mutations of the FGFR3 gene using PCR amplifi cation technique. Results: Nineteen cases were sporadic (95%) and one case had an affected father (5%). A paternal age above 35 years at the time of child’s birth was present in 7 cases (35%). Paternal exposure to occupational heat was noted in 6 cases (30%) and parental exposure to chemicals in 3 cases (15%). All cases showed typical clinical and radiological manifestations of achondroplasia. Anthropometricmeasurements quantitatively confi rmed the body physique in thestudied cases. G380R common mutations of the FGFR3 gene were detected in 15/18 cases (83%) with the G to A transition at nucleotide 1138 in 14 cases (77%). Agenesis of corpus callosum, not previously reported in association with achondroplasia, was present in the only case with the G-C transversio nmutation at nucleotide 1138 (5%).Conclusions: Awareness of the cardinal features of achondroplasia, properanthropometric measurements and detailed skeletal survey are the key foraccurate diagnosis, genetic counseling and avoidance of over diagnosis. The majority of studied Egyptian achondroplasia patients have the same common mutation that has been most often defi ned in patients with achondroplasia from other countries.Keywords: Achondroplasia, fi broblast growth factor receptor3,skeletal dysplasia, paternal heat exposure

Consanguinity and reproductive health among Arabs

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 depending on religion, culture, and geography. Arab populations have a long tradition of consanguinity due to socio-cultural factors. Many Arab countries display some of the highest rates of consanguineous marriages in the world, and specifically first cousin marriages which may reach 25-30% of all marriages. In some countries like Qatar, Yemen, and UAE, consanguinity rates are increasing in the current generation. Research among Arabs and worldwide has indicated that consanguinity could have an effect on some reproductive health parameters such as postnatal mortality and rates of congenital malformations. The association of consanguinity with other reproductive health parameters, such as fertility and fetal wastage, is controversial. The main impact of consanguinity, however, is an increase in the rate of homozygotes for autosomal recessive genetic disorders. Worldwide, known dominant disorders are more numerous than known recessive disorders. However, data on genetic disorders in Arab populations as extracted from the Catalogue of Transmission Genetics in Arabs (CTGA) database indicate a relative abundance of recessive disorders in the region that is clearly associated with the practice of consanguinity

Muenke syndrome with pigmentary disorder and probable hemimegalencephaly: An expansion of the phenotype

We describe a 2-year-old boy born to healthy, consanguineous parents. He had craniofacial asymmetry with left frontal bossing, midface hypoplasia, proptosis, and low-set ears. In addition, he had curly, light hair, and oval hypomelanotic patches in the abdomen, lower limbs and back and one hyperpigmented patch in the groin without acanthosis nigricans. Cranial three-dimensional CT scan showed right-coronal, sagittal, and lambdoid suture synostoses. His cranial MRI at 2-months of age showed left hemimegalencephaly, hypoplasia of corpus callosum, and an abnormal configuration of hippocampus. In spite of these cranial findings, he had mild developmental delay and his neurological examination showed symmetric strength, tone and reflexes. Apart from febrile seizures, there was no history of epilepsy. The proband developed asymmetric hydrocephalus at the age of 18 months that required third ventriculostomy. Post-operative cranial MRI showed Chiari I- like malformation and asymmetry of cerebral hemispheres but less dysplastic cerebral cortex. Mutation analysis of FGFR3 showed a c.749C > G, p.Pro250Arg substitution. To the best of our knowledge, these manifestations have not been reported in patients with Muenke syndrome

Consanguineous unions and child health in the State of Qatar

The aim of the study was to estimate the prevalence and sociodemographic predictors of consanguineous unions in the State of Qatar and to assess the association between consanguinity, fertility and child health. A representative sample of 1800 Qatari women aged >= 15 years was approached for the study. Of these, 1515 (84.2%) women agreed to participate. The consanguineous marriage rate was 54.0% with estimated population confidence limits of 52.3-55.7%. First cousin unions were the most common form of cousin marriage. The level of parental consanguinity (both in the respondent's parents and her parents-in-law) was quite high. In a multivariable analysis, both education of the respondent and her husband as well as parental consanguinity were found to be strong predictors of consanguineous unions in the index generation. Although fertility was high in both groups, the mean number of pregnancies was somewhat higher in respondents with first cousin unions. Concomitantly they also had a slighter higher rate of livebirths than women in non-consanguineous unions. The occurrence of asthma, mental retardation, epilepsy and diabetes was significantly more common in offspring of all consanguineous than non-consanguineous couples