•New pathogenic familial SMARCA4 variant, c.3081+1G>T.•Prophylactic surgery in healthy carrier of germline SMARCA4 mutation.•Long term hormone therapy in a 13-year-old girl.
Keywords: BRG1 protein; Prophylactic oophorectomy; SMARCA4 gene; Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT).