Anomaliile cromozomiale şi defectele orodentare – diagnosticul prenatal

Background

Genetic disorders can be classified as single gene inheritance, multifactorial inheritance, chromosome abnormalities and mitochondrial inheritance.

The medical management of individuals with syndromes affecting craniofacial and dental structures is mostly accomplished by an interdisciplinary team from early childhood on.

Structural morphogenetic defects – definitions
 

Every congenital structural defect in the body represents an inborn error in morphogenesis and may affect one or more systems. In general, most congenital anomalies can be divided into four types (Figure 1)⁽¹⁾:

a) Disruptions: a rare anomaly related to breakdown of the original normal foetal developmental process – e.g., craniofacial cleft resulting from amniotic bands.

b) Deformations: these occur secondary to mechanical forces, leading to anomalies of a lesser degree when compared to disruption – e.g., club foot, cleft palate, Pierre Robin sequence etc.

c) Malformations: a morphologic defect in an or­gan from an intrinsically abnormal developmental process – e.g., polydactyly, congenital heart anomalies, cleft lip etc. 

d) Dysplasia: an abnormal growth or development of a specific tissue or organ.

Genetic changes

The chromosomal abnormalities can be due to alterations in the number or structure of the chromosomes.

The chromosomal anomalies typically arise from alterations in the DNA containing chromosomal regions and can be reliably detected by karyotype analysis^(1,2,3).

Karyotyping is the basic tool of cytogenetic studies and most commonly involves G banding staining technique.

a) Numerical abnormalities

The most frequently reported numerical abnormalities are aneuploidies which may be due to either nondisjunction or anaphase lag (Figures 2 and 3)^(3,4).
 

b) Structural chromosomal abnormalities

Structural abnormalities are mostly caused spontaneously by loss or rearrangement of the chromosomal material⁽⁴⁾.
 

Chromosomal disorders and syndromes often arise from numerical and structural defects of the chromosomes, leading to various manifestations, some of which also include the craniofacial region.

Genetics and its understanding and applications enhance our ability to understand the growth and development of craniofacial structures, leading to the early intervention and prevention of disease onset^(2,4-6). Dental health caregivers should be aware of the technological and scientific improvements in the field of genetic testing and at the same time have ethical restraints over unrealistic expectations from it^(2,7,8).

Several chromosomal disorders, numerical and structural as well, include oro-dental defects among their clinical symptomatology (Table 1)^(10-50). The severity of these disorders vary widely from extremely severe to mild, but oral defects are present in all.
 

Discussion

The development of novel clinical therapies for orofacial and dental pathological conditions depends very much on a detailed knowledge of the molecular and cellular processes that are involved in head formation.

c) Clinical relevance of genetic findings

Currently, craniofacial abnormalities can be detected by modern ultrasound examination as early as at 16 weeks of gestation^(2,51). In oral clefts, which are particularly relevant to clinical dentistry, the only therapy available for the closure of the cleft(s) is the surgical intervention. The identification of the molecular players and the unraveling of the genetic pathways that dictate palatogenesis and lip formation could offer new and exciting possibilities for the prevention and therapy of orofacial defects^(1-8,51).

The knowledge of the genetic alterations that may cause oro-dental defects allows the genetic examination, prenatal diagnosis and the counseling of future parents with traits of oral cleft in the family.

Conclusions

The control of genetic diseases should be based on an integrated and comprehensive strategy combining the best possible treatment and prevention through community education, population screening, genetic counseling, and the availability of early diagnosis.

Genetic counseling will encompass legal and psychosocial management issues related to genetic screening, privacy and confidentiality, disclosure of unexpected and unwanted findings, and obligations to identify and communicate difficult issues.  

Compliance with ethics requirements:

The authors declare no conflict of interests regarding this article. The authors declare that all the procedures and experiments of this study respect the ethical standards in the Helsinki Declaration of 1975, as revised in 2008, as well as the national law. The informed consent was obtained from the patient included in the study. No funding for this study.