FISH STUDIES IN A PATIENT WITH SPORADIC ANIRIDIA AND T(7-11)(Q31.2-P13)

A 2 year old female presenting with bilateral sporadic aniridia was fo und to have an apparently balanced reciprocal translocation with a chr omosome 11 breakpoint within band p13. Fluorescence in situ hybridisat ion (FISH) studies with distal 11p13 specific cosmids showed that the chromosome 11 breakpoint lay between the aniridia (PAX6) locus and a r egion approximately 100 kb distal to PAX6 defined by the cosmid FO2121 . Although this patient did not have a detectable deletion within PAX6 , her aniridia may have resulted from a disruption of the distal chrom atin domain containing either enhancers or regulators for PAX6. This c ase may therefore be another example of aniridia caused by a position effect as recently described in two familial aniridia patients in whic h the phenotype cosegregated with chromosome abnormalities with 11p13 breakpoints.