Familial transmission of 5p13.2 duplication due to maternal der(X)ins(X;5)

Submicroscopic duplications of 5p13 have been recently reported in several cases, warranting the description of a new clinical entity (Chromosome 5p13 Duplication Syndrome; MIM 613174). These microduplications, while variable in size, all contain at least part of the NIPBL gene. Patients with duplications in this region present with intellectual disability/developmental delay (ID/DD) and dysmorphic facies. In addition, skeletal and brain abnormalities have been variably reported, as well as propensity for obesity in adulthood and hypotonia. We report a family with two affected sons and two affected daughters, each carrying a duplication at 5p13.2 encompassing the 3' portion of SLC1A3 and the 5' portion of NIPBL. Upon confirming the SNP microarray finding by FISH in the proband, it was discovered that the 5p13.2 duplication was located on the short arm of the X chromosome. Further FISH studies on the family demonstrated that all affected children and their mother carried a derivative X chromosome with insertion of material from 5p13.2 into the intermediate region of Xp [der(X)ins(X;5)(p2?2.1;p13.2p13.2)]. To our knowledge, this is the first report of an inherited duplication of 5p13.2 with multiple affected family members. This family underscores the need to confirm array findings by FISH, both in the proband and family members, to discern implications for pathogenicity and more accurately define the recurrence risk.