Pleiotropic effect of a novel mutation in GCNT2 causing congenital cataract and a rare adult i blood group phenotype.

Mutations in GCNT2 have been associated with the rare adult i blood group phenotype with or without congenital cataract. We report a novel homozygous frameshift mutation c.1163_1166delATCA, p.(Asn388Argfs*20) as the cause of congenital cataract in two affected siblings. Blood group typing confirmed that both affected males have the rare adult i phenotype, supporting the hypothesis that the partial association of I/i phenotype and congenital cataract is due to the differential expression of GCNT2 isoforms.