Genotypes and phenotypes of capillary malformation-arteriovenous malformation: characterization and correlation analysis.

Background: Capillary malformation-arteriovenous malformation (CM-AVM) is a rare genetic disorder characterized by multiple small capillary malformations (CMs) and arteriovenous malformations (AVMs), which has been linked with pathogenic variants in RASA1 and EPHB4. However, more data are needed to explore the phenotypic characteristics and the association between genotypes and clinical phenotypes.

Objectives: Our aim was to investigate the phenotypic and genetic characteristics of CM-AVM in East Asians, identify potential unique phenotypes, and conduct genotype-phenotype association analyses.

Methods: This is a single-center study prospectively collecting CM-AVM patients' clinical data, with genetic data from blood or tissue samples.

Results: A total of 59 patients were enrolled. Thirty-two individuals had a leading CM greater than Schobinger stage II. The trigeminal nerve branches and greater auricular, transverse cervical, and lesser occipital nerves' somatosensory innervation zones divided head and neck CMs into six zones: V1, V2, V3, GA, TC, and LO zones. GA, TC, and LO zones had a positive correlation with one another but a negative correlation with V2 zone involvement. The RASA1 and EPHB4 pathogenic variants were detected in 41 out of 59, which showed two types of variant allele frequency (VAF) distributions. VAF above 30% made RASA1 pathogenic variants more susceptible to multifocal CMs than those below 30%.

Conclusions: Leading CMs in the head and neck exhibit two segmentation patterns, anterior and lateral, which may differ in ear involvement and progression. Germline RASA1 pathogenic variants increased multifocal CM risk more than the somatic variants.