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The Features of Down Syndrome and the Risk of Parent’s Age

Background: Down syndrome is the most common autosomal disorder in humans. And the most common genetic chromosomal disorder causing mental disability in children. It also cause other medical abnormalities including heart and gastrointestinal disorder. These children sharing common features and characteristic faces. Each individual with this syndrome will not have all the features, but they will have a unique combination. Objective: In our study we try to spot light on the craniofacial features of Down syndrome in our country: their percentage; to compare it with another study in other countries. We also focus on the craniofacial features accuracy in diagnosis. Karyotyping not always available. Also we study the risk factors where we found that the mother age is not the only risk factor, but also the father age play a big role in Down syndrome and this risk factor needs to be studied with large number of patients. Also we study the problems associated with Down syndrome and its percentages, and to compare it with other study done in our neighbor's countries, where we found many differences Setting and Design: Our study is a descriptive, case series retrospective study was conducted in Benghazi Libya's children hospital. This study includes 73 patients who were referred to our Genetic clinic from October 2016 to march 2017. The genetic clinic is the only clinic in Benghazi and the whole East of Libya. Original Research Article Abdalrazi et al.; AJPR, 8(1): 12-18, 2022; Article no.AJPR.81821 13 This clinic follows children with DS and children with dysmorphic features in Benghazi and the Libyan ‘east. Materials and Methods: We studied 73 children randomly from different age group, and different socioeconomic classes, who attend the genetic clinic, which is an outpatient clinic and the only clinic which follows children with DS and dysmorphic feature in a pediatric hospital in BenghaziLibya. We took the history from the parent (the father and the Mother). The investigation done in our hospital. Father and mother age at pregnancy. Spontaneous or induced pregnancy. Drug history of the mothers and fathers. History of abortion and normal children. Any other baby with Down syndrome or other dysmorphic features. Echocardiography done for all children. Ultrasound abdomen and brain did for all children. Thyroid function test done for all children and repeated annually for all children. The diagnosis done mainly by clinical features. Some cases (40 cases) are proved by karyotype chromosomal analysis.


INTRODUCTION
Down syndrome is the most common autosomal disorder in human. And the most common genetic chromosomal disorder causing mental disability in children.
It also cause other medical abnormalities including heart and gastrointestinal disorder.
These children sharing common features and characteristic faces.
Each individual with this syndrome will not have all the features, but they will have a unique combination.
In 1862 an English physician john Langdon Down 1 st characterized DS as a distinct form of mental disability [1,2].
The cause of which was not known until 1959 where it was showed that this individual carried 47 chromosomes instead of 46 [1].
The extra chromosome labeled as the 21 st and the condition as trisomy 21.
The condition was referred to as mongolism till 1965 when the WHO dropped this reference after a request by Mongolian delegate.
And they supported Down syndrome [1]. DS is the most common autosomal disorder in human [3].
It occurs in all areas of the world and among all racial groups The typical humane karyotype is designed as:-46, XX typical for human female and 46, XY typical for human male [1].

What is Trisomy?
It is a chromosomal anomaly that is characterized by the presence of an extra chromosome in the cells of a person's body.
DS occur in approximately 1 in 700 of all live births.
However the incidence varies with the age of mother, the incidence for mother aged 25 years is 1 in 1400 and increases to 1 in 40 for mother aged 45 years [4].

Genetics of the Disease
The most common cause of having a DS babies is presence extra copy chromosome 21 resulting in trisomy. Non disjunction type ~95% of all cases.
The other causes can be Robertsonian translocation and isochromosomal or ring chromosome.
Ischromosome is a term used to describe a condition in which two long arms of chromosome separate together rather than the long and short arm separating together during egg sperm development [5,6].
Trisomy 21 (karyotype 47, XX, + 21 for females and 47, XY, + 21 for males) is caused by a failure of the chromosome 21 to separate during egg or sperm development [5].
In Robertstonian translocation which occurs only in 2-4% of the cases, the long arm of the chromosome 21 is attached to another chromosome (generally chromosome 14) [5].
Translocations account for 9% of the children with DS born to mothers under the age of 30 years [7].
The phenotype in translocation DS is not distinguishable from the regular trisomy 21DS [7].
While mosaicism deals with the error or misdivision that occurs after fertilization at some point during cell division.
Due to this people with mosaic DS have two cell lineages that contribute to tissues and organs of individuals with Mosaicism (one with the normal number of chromosomes, and other one with an extra number 21 [5,2].
The percentage of trisomic cells may vary between cells located in different parts of an individual's body.
For example, the percentage of trisomic cells in the muscles may be different from that seen in the brain cell or blood cells.

Features of Down Syndrome
Various conserved features are occurring in all DS populations, including learning disabilities, craniofacial abnormality and Hypotonia in early infancy [8].
DS individuals have variety of physical characteristics like a small chin, up slanted eye, poor muscle tone, a flat nasal bridge, a single crease of the palm and a protruding tongue due to a small mouth and large tongue [9].
Other features of Down syndrome;-Each individual with DS will not have all the features seen in these children, but they have a unique combination, The most common features are;-Characteristic facial appearance. Mild to moderate mental retardation. Congenial heart disease. Gastrointestinal problems. Increased cold and respiratory problems. Leukemia and Alzheimer.

MATERIALS AND METHODS
We studied 73 children randomly from different age group, and different socioeconomic classes, who attend the genetic clinic, which is an outpatient clinic and the only clinic which follows children with DS and dysmorphic feature in a pediatric hospital in Benghazi-Libya.
This study is a descriptive case series study, stated October 2016 and finished March 2017. We toke the history from the parent (the father and the Mother).
The investigation done in our hospital. Echocardiography done for all children.
Ultrasound abdomen and brain did for all children.
Thyroid function test is done for all children and repeated annually for all children.
The diagnosis done mainly by clinical features. Some cases (40 cases) are proved by karyotype chromosomal analysis.

RESULTS
Regarding the pregnancy and the family history;-Almost all the mother have spontaneous pregnancy, only two mothers use CLOMID to get pregnant.
One family had 3 children with DS and no normal children, One family have two children with DS, and three normal children One family had one child with neurofibromatosis part of twin with Down syndrome.
One family had twin one normal child and one Down syndrome.
On examination, we found;-

3-abdominal ultrasound done for all children the result is as;-
Two cases has nephrocalcinosis, 2.7%. One case has gallbladder stone 1.36%. One case has dilated pelvicalyceal system 1.36%

DISCUSSION
We compare our study with another one done in India where they study 524 patients over 7.5 years [10].
The result in that study was as follow;- GIT abnormalities as follow;-Imperforate anus 3 cases, Hirschsprung disease 2 cases, duodenal atresia one case and Morgagni hernia one case.
Some features almost have same percentages, and some others defers a lot.
Epicanthic folds is less than the half the other study [10].
The flat facial profile is one of the predominant feature in our study, and is only 50.9% in other study [10].
The CHD is more common in our baby with DS in compare to the other study [10,2].
Endocardial cushion defect also called as atrioventricular cushion defect is most common form which affects up to 40% of the patients. Ventricular septal defect (VSD) is also present in these population which affects up to 35% of the patients [11]. Also the GIT anomalies associated with DS is more common in our study;-Hirschsprung disease in our study is 4.1% and the other study [10] it is 0.38% only.
Duodenal atresia in our study is 2.74%. And in the other study [10] it is only 0.19%.
DS patients constitute 12% of all cases of Hirschsprung disease (HD).
Duodenal stenosis (DST) and imperforate anus (IA) are 260 and 33 times more likely to occur in DS [12].
HD is a form of low intestinal obstruction caused by the absence of normal myenteric ganglion cells in a segment of the colon [13].

CONCLUSION
All features of DS need not to be present in the same individual.
Almost all children diagnosed on clinical examination to have DS, are proved to have nondisjunction type of DS.
Only one case has mosaic DS.
Father age has a big role in DS as a major risk factor, and this should be studied in large number of patients.
The most common features which we found in high percentages are;-Mental retardation almost all patients have a degree of mental disability.
With major deference from other study in some features, and minor differences in others.

CONSENT
As per international standard or university standard, patients' written consent has been collected and preserved by the author(s).

ETHICAL APPROVAL
As per international standard or university standard ethical approval has been collected and preserved by the authors.