More than 130 mutations (changes) in the FOXL2 gene have been found to cause BPES. It has been reported that mutations that lead to a significantly shortened FOXL2 protein often cause BPES type I (characterized by eyelid malformations and premature ovarian failure (POF)), while mutations that result in an extra long FOXL2 protein may cause BPES type II (which involves only eyelid malformations). However, in a study published in 2003 in the American Journal of Human Genetics, the authors discussed how their study was the first to demonstrate intra- and interfamilial phenotypic variability (i.e. both BPES types caused by the same mutation). They discuss how assigning an affected family a diagnosis of either BPES type I or II is not always possible because of this. The article also discusses a previous report of menstrual abnormalities and reduced female fertility in two families with BPES type II, suggesting overlap between both BPES types, as well as a report of a family with BPES type I in which the first generations of affected females are infertile while three affected young women in the youngest generation appear to have normal pelvic ultrasound and hormone levels. They do caution that in this family, the early age of the affected women may preclude an accurate prediction of whether they will have POF, since the onset of POF usually occurs at a later age.
Approximately 12 percent of people with BPES do not have an identified FOXL2 gene mutation; the cause of the condition in these people is unknown, and therefore there is no information on whether there may be variation within families for these affected individuals.
Last updated: 6/6/2011
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