The predictive value of FISH analyses for possible occurrence of Wilms tumor in aniridia patients with/without chromosome abnormalities around 11p13. R. Muto^1,3, S. Yamamori², M. Osawa¹, H. Ohashi³. 1) Department of Pediatrics, Tokyo Womens Med. Univ., Shinjuku-ku, Tokyo Japan; 2) Research department Mitsubishi Kagaku Bio-Clinical Laboratories, Inc.Tokyo Japan; 3) Division of Medical Genetics, Saitama Children's Medical Center, Saitama Japan.
   Aniridia is an autosomal dominant condition caused by haploinsufficiency of the PAX6 gene at 11p13. The abnormalities of the PAX6 gene include mutations in the gene, position effect and gross deletions (cytogenetically visible or non-visible) around the gene. When gross deletions involve adjacent genes including WT1 (about 750 kb from PAX6 ), patients are predisposed to develop Wilms tumor and associated abnormalities (WAGR syndrome). We studied 17 patients with aniridia (10 are chromosomally normal and 7 abnormal) for possible deletion around 11p13 by FISH with four probes: PAX6, D11S2163 ,PER and WT1. Eight patients had gross deletions spanning the entire four loci, among whom 5 developed Wilms tumor, while none of the other 9 patients without detectable deletion have developed Wilms tumor. Four papers have been previously published to study microdeletions in the 11p13 region by means of molecular methods in aniridia patients. Out of a total of 101 patients in these five reports including this report, 29 patients had a deletion spanning from PAX6 to WT1 loci, of whom 14 developed Wilms tumor (48.3%). None of the other patients without deletion developed Wilms tumor. Risk assessment of Wilms tumor occurrence in aniridia patients by fine evaluation around the 11p13 region using FISH would be reliable and practical.