Clinical Genetics
Genetic counseling includes providing information to the family of individuals who have or are at risk of a genetic problem or congenital anomaly, planning the tests to be performed, determining/preventing the risk in the next generations, monitoring the problem and psychological support. If any genetic test has been performed, interpreting the test results and determining the risk of occurrence in other family members are also within the scope of genetic counseling.
In what cases is genetic counseling given?
Dysmorphology, which is briefly defined as “deformity”, is the abnormality of the morphological structure in living things and is the sub-branch of clinical genetics that deals with structural anomalies. There are some criteria that should be related to facial and body proportions as a result of taking the average of measurements made on a large number of individuals in populations. Almost all individuals diagnosed with genetic syndrome / genetic disease have minor and/or major dysmorphic findings in face-body ratios outside normal morphological limits (Table 1). For example, many facial and body/organ anomalies coexist in Down syndrome. Simian lines on the hand and Brushfield spots on the iris are examples of minor dysmorphic findings specific to this syndrome. Although major dysmorphic findings involving the limb and skull bones and muscles are not observed in this syndrome, organ anomalies may accompany them. The prevalence of minor anomalies in the population is approximately less than 4%.
Table 1. Some examples of minor and major dysmorphic findings
| Minor Dysmorphic Findings | Major Dysmorphic Findings |
|---|---|
| prominent ear | cleft lip-palate |
| dimple on cheek | Hypoplasia/aplasia of the extremities |
| simian line | anal atresia |
| cleft in the ear | cranium anomalies |
| Cleft in the tongue | Congenital heart anomalies |
The majority of major dysmorphic anomalies occur as congenital malformations. Although these malformations occur as a result of chromosomal disorders, single gene disorders (mutations) or teratogens, there may be cases where a genetic cause cannot be elucidated. Approximately 2-3% of all newborns have major congenital structural anomalies. The majority of these can be detected by detailed fetal USG follow-ups in the prenatal period. Congenital anomalies may occur in isolation or in a unique combination affecting more than one organ system. Congenital single primary defects are divided into 4 main headings according to the mechanism of formation: malformation, deformation, disruption and dysplasia.
Malformation: It occurs as a result of morphogenesis not progressing normally due to intrinsic/structural problems in the developing organ (organogenesis). It begins to be noticed as permanent structural and/or functional disorders in the prenatal period. Since organogenesis is completed in the 8th week, malformation errors mostly occur before this period. Etiology includes chromosomal disorders, single gene diseases, multifactorial inheritance and teratogen exposure. Example: congenital heart anomalies, cleft palate/lip, neural tube defects, esophageal atresia, anal atresia.
Deformation: It is caused by the deterioration of normally developing structures as a result of mechanical (extrinsic) effects, especially in the prenatal period. It mostly occurs in the period after organogenesis occurs (after the 8th week). Example: congenital hip dislocation, pes equinovarus, craniofacial anomalies. Mechanical causes include conditions such as maternal obesity, oligohydramnios, twin-multiple pregnancy.
Disruption: It is the permanent deformation of a normally developing structure/organ as a result of destruction (destruction, damage). Among the reasons for destruction: Drugs such as amniotic tape, thalidomide, and blood supply problems can be listed. Disruption examples: limb amputations, facial clefts, gastroschisis, embryopathies.
Dysplasia: It is a structural disorder that occurs due to organizational defect of cells of a certain tissue type. Main heading examples such as ectodermal dysplasias and skeletal dysplasias can be given. They mostly occur due to single gene disorders.
The incidence of all genetic diseases in live births is approximately 8-10%. Family history is very important when approaching a dysmorphic case. Mother and father phenotypes (physical appearances) must definitely be seen. A detailed family tree should be drawn. In some defined genetic syndromes, specific dysmorphic findings should be closely monitored (for example, mane and neck are typical for Turner and Noonan syndromes; flattened nasal root and heart anomalies are typical for Down syndrome). In dysmorphic cases, all organ systems should be scanned. Chromosome analysis, FISH analyses, array CGH analyzes and/or genetic tests for single gene diseases for diagnosis
You can contact us to get information about our genetic tests, consultancy services and more.
Contact Us
Clinical Genetics
Cytogenetics
Molecular Cytogenetics
Molecular Genetics
Bioinformatics
Scientific Project Services