الفهرس 
Genetic Disorders
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Abstract
Genetic risk of disease is an important component of overall risk of such disease in addition to environmental, socio-economic, and behavioural risk factors. Therefore, predicting the genetic risk of a disease for an individual is a powerful tool in taking preventive measures against the occurrence of the disease. The important role of genetics in pediatric illness has been increasingly recognized, but the true impact has not been well delineated.
Though individual genetic disorders are collectively rare, yet more than 19,000 recognized genetic disorders had been identified. Studies showed that at least 2% of newborns have a major congenital abnormality; about 1% has unifactorial disorders and about 0.5% has major chromosomal abnormalities.
In order to study the contribution of genetic disorders among the pediatric inpatients, we evaluated 850 pediatric patients admitted to Alexandria University Paediatric hospital during the period March 2011 - August 2011. The following results were obtained. The present study, showed remarkable contribution of genetic disorders among the pediatric admissions (40.2%) especially after addition of those cases in which the underlying genetic role was not specifically delineated in spite of the presence of genetic evidence (17.5%).
Mendelian disorders was the most frequent (22.4%) distributed as follows; Autosomal Recessive 18 %, Autosomal Dominant 2% and X-linked disorders 2.4 % , Genetic Uncertain group constituted (17.5%) and followed by multifactorial disorders (15.7%). The least frequent disorders were those resulted from chromosomal aberration disorders (2.2%).
There was slight increase of the percentage of male patients among the environmental conditions (42.9%) than the genetic / multifactorial conditions (38.8%). However, lumping of the genetic / multifactorial conditions and genetic uncertain conditions together (57.1%) make the male sex slightly predominant among genetic groups. Female sex was predominant among the genetic / multifactorial group irrespective of adding the percentage frequency of the genetic uncertain group.
Two third of the selected sample was either low middle / middle social classes (40.8% and 27.3% respectively). High social class was slightly higher among the environmental conditions compared with the genetic / multifactorial conditions (43.9% vs. 41%). In the mean time, genetic / multifactorial conditions were found higher in the high middle social class compared with the environmental conditions (42.2% vs. 36.7%). No statistical significant was observed.
Most of the parental ages (maternal and paternal) in the present study were young (92.6% and 88.2 % respectively). This finding will eliminate the effect of parental age as an associated risk factor in causation of genetic disorders or environmental conditions. In addition, there was slight unremarkable increase of the percentage frequency of young parents (maternal and paternal) among both environmental and genetic / multifactorial groups (41.7% vs. 39.7% and 41.4% vs. 40.5% respectively). Old parental age groups were not present in the present study and as a result of this effect, the actual expected parental age effect will disappear and neutralized. Several studies had shown the association of advanced paternal and maternal age.
Although the parity of the mother’s patients might affect the occurrence of some genetic disorders due to the advances of parental age especially maternal age. Yet, in the present study, most of the cases (84.9%) resulted from the first birth orders – third birth order which is usually associated with the young maternal age of their mothers (92.6%).
The present study showed that consanguineous parents were found among 39.8% which was slightly more than that recorded previously. In addition paternal parents and maternal parents consanguinity were recorded among more than one fifth of the selected sample. On the other hand, the frequency of consanguineous marriages was higher among the genetic / multifactorial group (43.2 %) than the environmental group (35.2%). This difference was statistically significant (X2(2)=8.631, P=0.013). Also both maternal and paternal parent’s consanguinity were predominant among the genetic group (39.2% vs. 43.2 % and 38 .1 % vs. 44.6 %).
On the other hand seasonal variation was not observed in the present study. No statistical difference was found between the different seasons of conception and final diagnosis. This was expected where genetic diseases are almost not associated with seasonal variation like environmental disorders.
Studying the mode of delivery revealed that abnormal deliveries among the genetic / multifactorial conditions (43.1%) were slightly high if it is compared with those among the environmental conditions (40.7%). However the difference was not statistically significant
On the other hand, prematurely was found predominant among the genetic / multifactorial conditions followed by term deliveries. In the meantime low birth weight births were higher among the genetic / multifactorial patients (48.2%) than those among the environmental conditions (31.4%) The difference between those groups was statistically significant (X2(4)=11.723, P=0.020).
It was found that about one third (31.2%) of the selected sample had positive history of one abortion or more. The occurrence of abortion among the environmental group was higher than that among the genetic / multifactorial group. Yet the difference was statistically insignificant P=0.099. On the other hand, negative history of still births was equally distributed among both environmental and genetic / multifactorial groups (41.5% vs. 40.7% respectively). However the existence of still births among genetic / multifactorial group was almostly double that among the environmental group (50% and 28.6% respectively). This difference however was not statistically significant (X2(2) = 1.882, P=0.390)
Studying the linear growth of the selected sample revealed that 40.1% had abnormal weight, 36.6% had abnormal height and 27.7% had abnormal head circumference. Patients with abnormal weight (>3rd centile and <97th centile) were more common among the genetic / multifactorial group than the environmental group. In the meantime, the percentage frequencies of abnormal heights and abnormal head circumference were more common among the genetic / multifactorial group (50% and 42.9% vs. 31.9% and 41.4%) for the height centiles and (47.3%, 43.1% vs. 28%, 41.2%) for head circumference centiles. The difference for weight centiles was not significant (X2(4)=5.269, P=0.261) while the differences in height and head circumference centiles were statistically significant (X2(4)=22.556, P=0.000) and (X2(4)=18.362, P=0.001) respectively.
In conclusion, there seems that no doubt that nowadays especially in developed countries; genetic disorders contribute significantly to morbidity and mortality. The vast majority of genetic disorders are serious and some of them are lethal, few are completely curable and relatively few are treatable. Despite a general fall in the perinatal mortality rate.