Patients with an inherited autosomal-dominant disorder, capillary malformation-arteriovenous malformation (CM-AVM), frequently have mutations in Ras P21 protein activator 1 (RASA1). The aims of this study were to determine the prevalence of germline RASA1 variants in a French multicentre national cohort of children, age range 2-12 years, with sporadic occurrence of capillary malformation (CM) of the legs, whatever the associated abnormalities, and to identify genotype-phenotype correlates. DNA was extracted from leukocytes in blood samples, purified and amplified, and all exons of the RASA1 gene were analysed. Among 113 children analysed, 7 had heterozygous variants (6.1%). Four different variants were identified; 2 were new. In children with RASA1 variants, CMs were more frequently bilateral and multifocal. In conclusion, RASA1 variants are rarely found in children with sporadic CM of lower limbs without CM-AVM syndrome. CMs in this study were heterogeneous, and no disease-causing relationship could be proven.

ABF measured by Duplex ultrasonography is a simple, low-cost and noninvasive complementary examination for help in detecting LLD, with a difference of ≥ 50% possibly associated.