P350: ELMO2-related primary intraosseous vascular malformation: New diagnosis and phenotypic expansion of an ultra-rare vascular anomaly syndrome

Notably, KCNQ1 resides in a cluster of imprinted genes on chromosome 11p15.5,with the imprinting control region 2 (IC2) implicated in Beckwith-Wiedemann syndrome and Russell-Silver syndrome being located within the KCNQ1 locus.It has been previously demonstrated that KCNQ1 is upregulated in gingival tissues of patients with hereditary gingival fibromatosis (HGF) via RAS/MAPK/AP-1 signaling, although the prevalence of KCNQ1 coding variants in cases of HGF is unknown.Case Presentation: Here we describe a 9-year-old Guatemalan male who presented to genetics at age 6 years due to family history of unbalanced 14;16 translocation in his sister and several maternal relatives.On physical examination he was noted to have significant gingival overgrowth, obscuring visibility of a majority of his dentition and significantly impacting dietary capabilities and overall quality of life.He was additionally noted to have -3SD short stature.There was no reported family history of similar gingival findings.Diagnostic Workup: He was not found to harbor the familial translocation but given clinical findings trio exome sequencing was performed which identified a heterozygous variant in KCNQ1, specifically c.347G>T, p.(R116L), interpreted as a variant of uncertain significance by performing laboratory.Given clinical presentation in conjunction with available literature, a provisional diagnosis of KCNQ1-related gingival fibromatosis with pituitary dysfunction was made.The variant was inherited by his mother, an obligate balanced 14;16 translocation heterozygote who demonstrated short stature but no history of gingival fibromatosis or other reported medical concerns.