Patient with Terminal 9 Mb Deletion of Chromosome 9p: Refining the Critical Region for 9p Monosomy Syndrome with Trigonocephaly

We describe a patient with typical manifestations of 9p monosomy syndrome, including trigonocephaly and sex reversal. Array comparative genomic hybridization (CGH) revealed a 9p terminal deletion of approximately 9 Mb with the breakpoint at 9p23. We compared the deleted segments of 9p associated with reported cases of 9p monosomy syndrome with trigonocephaly. We did not identify a region that was shared by all patients; however, when only pure terminal or interstitial deletions that did not involve material from any other chromosome were compared, we identified a segment from D9S912 to RP11-439I6 of approximately 1 Mb that was deleted in every patient. We propose that this 1-Mb segment might be the critical region for 9p monosomy syndrome with trigonocephaly.