Biallelic variants in BRCA1 gene cause a recognisable phenotype within chromosomal instability syndromes reframed as BRCA1 deficiency

Pathogenic variants in BRCA1 gene in heterozygous state are known to be associated with breast-ovarian cancer susceptibility; however, biallelic variants cause a phenotype recognised as Fanconi anaemia complementation group S. Due to its rarity, medical management and preventive screening measures are insufficiently understood. Here, we present nine individuals (one new and eight previously presented) with biallelic variants in BRCA1 gene, to...