Proximal interstitial 1p36 deletion syndrome: the most proximal 3.5-Mb microdeletion identified on a dysmorphic and mentally retarded patient with inv(3)(p14.1q26.2).

From the investigation by microarray-based comparative genomic hybridization (aCGH), a new syndrome with "atypical" proximal interstitial deletion of 1p36.23-36.11 has been suggested. Here, we report on an 8.5-year-old girl with psychomotor developmental delay and a dysmorphic appearance. Although her G-banded chromosomal analysis showed inv(3)(p14.1q26.2), detailed FISH analyses denied pathogenic deletions around the breakpoints of chromosome 3. Accordingly, aCGH analysis was performed to identify a genomic aberration related to her phenotype, and a 3.5-Mb interstitial deletion of 1p36.13-36.12 was revealed. This deletion was the most proximal interstitial deletion of 1p36. Compared to the previously reported patients, abnormally shaped teeth, delayed tooth eruption, and leg malformation are unique phenotypes only to this patient, which might be due to the centromeric unique deletion region with 0.8-Mb.