Hypotrichosis-lymphedema-telangiectasia syndrome: Report of ileal atresia associated with a SOX18 de novo pathogenic variant and review of the phenotypic spectrum.

Hypotrichosis-lymphedema-telangiectasia syndrome (HLTS) is a rare condition caused by pathogenic variants in the SOX18 gene. SOX18 plays a key role in angio- and lymphangiogenesis due to its expression in venous endothelial cells from which the lymphatic system develops. It is also expressed in embryonic hair follicles, heart, and vascular smooth muscle cells. The main clinical symptoms of HLTS include sparse hair, alopecia totalis, lymphedema, most often affecting lower limbs, and telangiectatic lesions. Only 10 patients with a SOX18 pathogenic variant have been described that presented with additional features such as hydrocele, renal failure, arterial or pulmonary hypertension, aortic dilatation, and facial dysmorphism. Here, we summarize these phenotypic variations and report an additional HLTS patient, with a 14-nucleotide de novo duplication in SOX18 and congenital ileal atresia, a feature not previously associated with HLTS.