Genetic Factors That Affect Asymmetric Mandibular Growth—A Systematic Review

Alicja Babczyńska,Michał Sarul,Beata Kawala

doi:10.3390/sym14030490

Abstract

Facial asymmetry is a feature that occurs to a greater or lesser extent in the general population. As its severity is usually slight, facial asymmetry may not be noticeable to the patient. However, there are cases when severe facial asymmetry not only affects the facial aesthetics by distorting facial proportions, but also contributes to problems related to the function of the stomatognathic system. The nodal signalling pathway appears to be of particular importance in the process of mandibular asymmetry, as it affects not only structures formed from the first pharyngeal arch, but also other organs, such as the heart and lungs. Following the evaluation of the available literature, the inheritance of mandibular asymmetry is a very complex and multifactorial process, and the genes whose altered expression appears to be a more important potential aetiological factor for asymmetry include PITX2, ACTN3, ENPP1 and ESR1. This systematic review attempts to systematise the available literature concerning the impact of signalling pathway disruption, including the disruption of the nodal signalling pathway, on the development of mandibular asymmetry.

Highlights

Facial asymmetry is a feature that occurs to a greater or lesser extent in the general population
A certain problem in the Nicot et al (2014) study was the exclusion of one patient with symmetry from the control group, as the principal component analysis (PCA) revealed that the patient had the largest difference in terms of global gene expression compared to the ten remaining patients
The most frequent keywords used during the analysis of selected articles were nodal signalling pathway and the PITX2 gene, which were considered to play a major role in asymmetry formation

Summary

Introduction

Facial asymmetry is a feature that occurs to a greater or lesser extent in the general population. In Obwegeser’s opinion [4], the causes of asymmetry can be divided into three groups according to the time of onset: those occurring in the process of embryogenesis, those occurring postnatally and those resulting from faulty growth regulation of unknown aetiology. Asymmetry can be caused by either unilateral hypoplasia or aplasia of the condylar process, unilateral hypoplasia or aplasia of the mandible, unilateral hypoplasia of the mandible and face, or hyperplasia of the entire half of the face, or underdevelopment of half of the face. As a consequence of the underdevelopment of the condylar process and the reduced height of the rami mandibulae, several significant abnormalities may occur, e.g., in the course of the occlusal plane, and cause several types of defects, the treatment of which can be a challenge for orthodontists and maxillofacial surgeons

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