Familial 1p36.3 microduplication resulting from a 1p-9q non-reciprocal translocation.

Unlike the 1p36 microdeletion syndrome, which has been extensively described, 1p36 microduplications have rarely been reported. We describe a three years old boy presenting with a severe global developmental delay and a few dysmorphic features. Cytogenetic analyses revealed a maternally inherited 3.35 Mb microduplication of chromosomal band 1p36.3. The maternal grandfather is also carrier of the same chromosomal rearrangement. Interestingly, the duplicated 1p36.3 segment was found to be localized at the telomeric end of the long arms of a chromosome 9, probably deriving from a 1p36.3-9qter non-reciprocal translocation. This particular type of chromosomal translocation has rarely been reported, and its mechanism is unclear. The phenotypical features associated with 1p36.3 microduplication vary due to the non-recurrent breakpoints of the rearrangements in this particular region. However when compiling the few described cases the phenotypical spectrum seems to include mainly developmental delay, mild facial dysmorphism, and neurological, cardiac and skeletal anomalies. The description of new patients carrying a 1p36.3 duplication like ours will lead to further delineation of the phenotypical spectrum and may help to find critical regions and causative genes implicated in the phenotype.