Screening of a large cohort of blepharophimosis, ptosis, and epicanthus inversus syndrome patients reveals a very strong paternal inheritance bias and a wide spectrum of novel FOXL2 mutations

Blepharophimosis, Ptosis, and Epicanthus inversus Syndrome (BPES) is caused by autosomal dominant mutations in FOXL2. There are two forms of BPES: type I (with primary ovarian insufficiency (POI)) and type II (without POI). Data are presented from a large cohort of 177 BPES probands. Diagnostic testing identified a wide range of mutations in 119 mutation-positive patients (including 38 novel mutations). Although FOXL2 mutations are distributed throughout the gene, over 50% were frameshift mutations within a hotspot region of the gene that can be detected using a single primer pair to provide a cost-effective and rapid screening method. There was a significant proportion of de novo cases in this study, although in 7% there may be undetected parental mosaicism. There was an excess of female compared to male probands and a highly significant bias in the parental original of inherited mutations, with 20/21 found to be paternal in origin (95%). This could be because BPES in a female is more likely to come to clinical attention and because there is a generalised and more widespread clinical effect on fertility, in addition to the established association with POI. This study demonstrates the importance of cascade screening and provides new information on inheritance and parental mosaicism in BPES which will aid genetic counselling and accurate risk management.