Vascular Mechanisms in the Etiology of Hemifacial Microsomia: A Systematic Review of Epidemiological, Clinical, and Genetic Evidence

Background: Hemifacial microsomia (HFM) is a congenital craniofacial malformation characterized by unilateral hypoplasia of structures derived from the first and second pharyngeal arches. Although the phenotype is well described, the underlying etiology remains incompletely understood. Disturbances in embryonic vascular development have long been proposed as a potential mechanism contributing to the characteristic unilateral craniofacial phenotype. Methods: A systematic literature review was conducted following PRISMA guidelines. Searches were performed in PubMed, Embase, Web of Science, and CINAHL to identify studies investigating vascular mechanisms in hemifacial microsomia and related craniofacial microsomia phenotypes. Evidence from epidemiological, clinical, radiological, and genetic studies was synthesized narratively because of methodological heterogeneity. Results: Of 450 screened records, eight studies met the inclusion criteria. Epidemiological studies identified associations between HFM and maternal factors potentially affecting embryonic perfusion, including vasoactive medication exposure, maternal diabetes, multiple gestations, and second-trimester vaginal bleeding. Population-based data further demonstrated an increased prevalence of single umbilical artery and growth restriction among affected infants. Clinical and radiological observations described regional vascular abnormalities, including carotid artery attenuation. One genetic association study suggested interactions between pathways involved in vascular development and neural crest cell biology. Conclusions: The available evidence is consistent with a possible contribution of disturbances in vascular development to the pathogenesis of hemifacial microsomia, particularly in unilateral presentations. However, current evidence remains indirect and heterogeneous. Vascular mechanisms may interact with genetic susceptibility and neural crest cell biology within a broader multifactorial developmental framework. Further studies integrating genomic analyses, developmental models, and detailed vascular imaging are needed to clarify the role of vascular mechanisms in craniofacial microsomia.