Microdeletion 22q11.2: clinical data and deletion size

Editor—Ninety probands with microdeletion 22 were ascertained at The Hospital for Sick Children, Toronto, between 1 January 1994 and 1 June 1997. All patients had been karyotyped by G banding and were found to have a 46,XX or 46,XY karyotype except for one patient who had a de novo unbalanced translocation: 45,XY,der(6) t(6;22)(p25;q11.2)/45,XY,der(6)t(6;22)(p25;q11.2),+f. The fragment was very small and was not defined. All were shown by FISH analysis to be deleted for D22S75 using probe N25 (Oncor, Gaithersburg, MD). FISH analysis for D22S75 was also performed on 126 parents of 73 probands. The study was approved by the Research Ethics Board of the hospital and written informed consent was obtained. Clinical data were reviewed retrospectively in 90 cases. Forty five (50%) were female and 45 (50%) male. The median age at diagnosis was 5.5 years, with 23 cases (26%) under the age of 1 year. The height in relation to age was lower than average, with 69/85 cases (81%) being less than the 50th centile (no data in five cases). Head circumference was less than the 50th centile in 56/80 cases (70%) (no data in 12 cases). Data on palatal abnormalities/hypernasal speech were available in 72 cases with no data in 18 cases. Palatal abnormalities/hypernasal speech were found in 55/72 cases (76%): 28 patients had hypernasal speech without cleft, four …