Congenital cataracts in females caused by BCOR mutations; report of six further families demonstrating clinical variability and diverse genetic mechanisms

• Published in: European journal of medical genetics 2020-02, Vol.63 (2), p.103658-103658, Article 103658
• Main Authors: Redwood, A., Douzgou, S., Waller, S., Ramsden, S., Roberts, A., Bonin, H., Lloyd, I.C., Ashworth, J., Black, G.C.M., Clayton-Smith, J.
• Format: Article
• Language: English
• Subjects: BCOR; Congenital cataracts; Oculofaciocardiodental syndrome; OFCD; X-linked dominant
• ISSN: 1769-7212; 1878-0849
• DOI: 10.1016/j.ejmg.2019.04.015

Pathogenic variants in the BCOR gene have been identified in males with X-linked recessive microphthalmia and in females with X-linked dominant oculofaciocardiodental (OFCD) syndrome. This latter condition has previously been regarded as rare but the increased availability of genetic testing in recent years has led to the identification of a greater number of patients. We report the clinical and molecular findings in a series of 10 patients with pathogenic BCOR variants from 5 families, all seen in a single institution over a two year period. We emphasize the phenotypic variability in this cohort and the diverse genetic mechanisms involved which included point mutations and deletions of BCOR as well as the occurrence of gonadal and somatic mosaicism. In this report we demonstrate the novel findings of four newly identified variants in BCOR associated with an OFCD phenotype, and suggest that the frequency of this condition in females presenting with congenital cataract, including unilateral cataract, is more common than anticipated. We demonstrate the utility of screening for genetic causes of congenital cataract. Although gonadal mosaicism in OFCD had previously been reported, we demonstrate the presence of somatic mosaicism where BCOR mutations may only be detected in DNA from tissues other than blood such as buccal cells. This study further delineates the clinical phenotype of the X-linked oculofaciocardiodental (OFCD) syndrome caused by BCOR gene abnormalities. Our families demonstrate novel molecular findings and important genetic mechanisms.