Any hereditary breast ovarian cancer syndrome in which the cause of the disease is a mutation in the BRCA1 gene. The disease is breast-ovarian cancer, familial, susceptibility to, 1 (Monarch Disease Ontology identifier MONDO_0011450). Also known as: BRCA1 hereditary breast ovarian cancer syndrome, breast-ovarian cancer, familial, 1, multifactorial, breast-ovarian cancer, familial, susceptibility to, type 1, hereditary breast ovarian cancer syndrome caused by mutation in BRCA1.