الفهرس 
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Abstract
GDD/ID is characterized by significant limitations in intellectual functioning and adaptive behavior, and is frequently associated with developmental delay and various congenital abnormalities. It has a significant impact on the affected person’s life, his family, and society, and it is a relatively common disorder.
A wide range of environmental factors, in addition to genetic determinants, can affect brain development. This can occur prenatally, perinatally, or postnatally. Teratogenic exposures, perinatal asphyxia, prenatal and postnatal infection, and nutritional inadequacies are the risk factors responsible for the greatest number of cases worldwide.
Because of the significant clinical and genetic heterogeneity, studying intellectual disability is challenging. Intellectual disability can be caused by both genetic and environmental factors that affect the nervous system’s development and function. Although environmental exposures can cause intellectual disability, genetic defects account for the majority of cases. Still, around ≈ 60% of cases of Intellectual disability do not have a known etiology.
A detailed history, full physical examination, and laboratory screening tests are all part of the systematic assessment of a child with intellectual disability. In patients with idiopathic non-syndromic intellectual disability, karyotype is considered the traditional diagnostic test for genetic assessment. Screening tests, metabolic testing, TORCH screens, and neuroimaging are some of the other available diagnostic tests, however they all have limited diagnostic utility.
Chromosomal analysis using the classical cytogenetic studies is considered the standard method for investigating syndromes suspected to have a chromosomal etiology, although it cannot discover chromosomal abnormalities smaller than 5-10 Mb. Microdeletions/ microduplications and subtelomeric rearrangements that disrupt genes can cause intellectual disability.
FISH with specific probes has been used in most molecular investigations focusing on copy number variant in patients with GDD/ID. Because FISH is costly, time-consuming, and labor-intensive, various alternatives have been tried. from these methods MLPA, is a very promising technique. MLPA is a sensitive and reliable technique for the detection of copy number variants. It is molecular genetic technique that identifies copy number variance, such as duplications or deletions.
In patients with GDD/ ID, we recommend starting with a cytogenetics study. If no abnormalities are found, move on to MLPA, a targeted test that may screen a large number of GDD/ID patients in a short time at a reasonable cost. Proceed to array CGH if no abnormality is detected by MLPA.
The aim of our study was to determine the possible role of maternal lifestyle and exposure to environmental risk factors in the development of intellectual disability and to detect chromosomal aberrations and/or copy number variants using various cytogenomics techniques in pediatric patients with intellectual disability.
This study was conducted on 40 selected patients who had intellectual disability attending Genetic Clinic, Pediatric Hospital, Ain Shams University and Outpatient clinics of the Clinical Genetic Department, National Research Center during the period from September 2018 to July 2020.
Inclusion criteria:
1) Intellectual disability (IQ below 70 / global developmental delay)
2) Both sexes
3) Pediatric patients under 18 years.
Exclusion criteria:
Trisomy 21.
40 apparently healthy children under 18 years of age was included as a control group
All patients were subjected to the following:
a) Clinical Evaluation:
1. Medical history:
• Full history taking including past, family history and pedigree analysis.
• Patients’ mothers were subjected to a questionnaire for assessment of environmental risk factors and maternal life style.
2. Physical examination:
General physical examination was done for all patients including anthropometric measurements at the time of clinical assessment as regard to weight, length/height and head circumference.
b) Laboratory methods:
1. Cytogenetic Studies: Samples were cultured and prepared for chromosomal analysis of blood lymphocytes using GTG-banding technique. Karyotype description was done according to the (ISCN).
2. DNA extraction: DNA extraction by PAXgene DNA purification kit and measurement of quality and concentration of DNA (PreAnalytix, Hiden, Germany).
3. Multiplex Ligation-dependent Probe Amplification (MLPA) (MRC-Holland 2002): The MLPA assay was performed using the SALSA MLPA probemix P245 for microdeletion syndromes screening and SALSA MLPA probemix P070 for screening of Subtelomeric regions. MLPA analysis was carried out as recommended by the manufacturer.
4. Fluorescence in situ hybridization (FISH) was carried out on selected case.
5. Array comparative genomic hybridization was done for selected case according to clinical presentation using Affymetrix Genome-Wide Human Array 6.0, Thermo Fisher Scientific, UK
The results showed that:
Out of 40 selected patients with GDD/ ID with or without multiple congenital anomalies (MCA), 20 patients (50%) had GDD, 8 patients (20%) had mild intellectual disability, 9 patients (22.5%) had moderate intellectual disability and 3 patients (7.5%) with severe intellectual disability.
History of positive parental consanguinity in 23 patients representing 57.5%, family history of ID in 23 patients representing 57.5% and family history of miscarriage in 8 patients representing 20%. On examination facial dysmorphic features (e.g.; frontal bossing, dolicocephaly, fascial asymmetry, low ant hairline, long lashes, arched eyebrows, synophoros, epicanthal folds, hypertelorism, hypotelorism, depressed nasal bridge, anteverted nostrils, peaked nose, cupped ears, low set ears, long or short philtrum and cleft lip and palate) were noted in 38 patients representing 95%, non-facial dysmorphic features (e.g. brachydactyly, arachnodactyly, simian creases, overriding toes and dysplastic nipples) were ssen in 30 patients representing 75%, other congenital anomalies (e.g. congenital heart diseases, brain anomalies, umbilical/ inguinal hernia and unilateral renal agenesis) were detected in 31 patients representing 77.5%, abnormal growth including low birth weight, failure to thrive and stunted growth in 13 patients representing 32.5%, short stature in 11 patients representing (27.5%) and convulsions in 2 patients representing 5%.
Different cytogenomics techniques conducted on our patients revealed normal karyotype in 39 patient representing 97.5% and 1 female patient representing 2.5% had abnormal karyotype described as 46,XX,add(18)(q23). MLPA subtelomeric screening, using P070 probemix and microdeletion/ microduplication screening using P245 probemix, was done for all patients.
Subtelomeric abnormality was detected solely in the patient with abnormal karyotype. Her subtelomeric screening revealed deletion 18q subtelomere. No other subtelomeric aberrations were detected in the other 39 (97.5%) patients with normal karyotype. Screening for microdeletion/ microduplication for all patients revealed 4 positive patients representing 10%. One patient had 5q35.3 deletion causing Sotos syndrome. Two patients had 22q13 deletion causing Phelan-McDermid syndrome. One patient had 15q11.2 deletion causing Prader-Willi syndrome. Thus, total positive cases by MLPA were 5 patients representing 12.5%.
In our study we combined MLPA and CMA in one patient. Our limitation to apply that for more cases was the high cost of array. We reported a female patient with GDD. Her karyotype revealed 46,XX,add (18)(q23). Both parents had normal karyotype. MLPA for the patient indicated deletion of 18q subtelomere, FISH analysis also revealed deletion of 18q subtelomere, and whole chromosome paint (WCP) associated with inverted DAPI indicated that all the duplicated segments originated from chromosome 18 and there was inversion of 18q segment. Array CGH identified 55.8-Mb duplicated segment and 614-kb deleted terminal 18q. Single nucleotide polymorphism (SNP) analysis for the patient and the parents revealed that the duplicated and deleted 18q regions originated from paternal chromosome 18. These findings suggested that the event occurred during paternal meiosis or early postzygotic stage.
In our study, pregnancy and delivery circumstances revealed that 5 patients were preterm representing 12.5%, 10 patients presented with low birth weight (35%), post-natal asphyxia in 7 patients representing 17.5%, post-natal cyanosis in 6 patients representing 15%, prenatal history of vaginal bleeding in 3 patients representing 7.5%, prenatal maternal infections and fever in 15 patients representing 37.5%, maternal gestational diabetes mellitus (GDM) in 3 patients representing 7.5%. Maternal history of chronic diseases including diabetes mellitus (DM), hypertension and asthma was found in 7 patients representing 7.5%, paternal history of chronic diseases in 7 patients representing 17.5%, prenatal maternal vomiting in 27 patients representing 67.5%, maternal history of drug intake including analgesics, antibiotics and antipyretics in 12 patients representing 30%, history of maternal exposure to different hazards including; ultrasound in 28 patients representing 70%, X-rays in 2 patients representing 5%, home paints in 3 patients representing 7.5%, insecticides in 2 patients representing 5%. Pre pregnancy BMI was 25.82 ± 3.94 with maternal increase in weight during pregnancy (˃15 Kg) in 5 patients representing 12.5%.
No mothers were found to be smokers, while 75% of fathers were smokers, no history of alcohol consumption was detected in both parents, 100% of mothers reported intake of folic acid during pregnancy, and maternal physical activity was reported to be mild in 45% and moderate in 55%.
In our study statistical significance differences between patients and controls were found in terms of distribution of gender and residency, the percentage of mothers taking coffee, fathers taking shisha, and fathers consuming soft drinks, the percentage of mothers facing microwave and ultrasound radiations, children birth weight, post-natal asphyxia and post-natal cyanosis and family history of intellectual disability.