Report of a patient and further clinical and molecular characterization of interstitial 4p16.3 microduplication.

Background: Pure interstitial duplications of chromosome band 4p16.3 represent an infrequent chromosomal finding with, to the best of our knowledge, only two patients to date reported.

Case Presentation: We report on a 13-year-old boy showing a set of dysmorphic facial features, attention deficit hyperactivity disorders, learning difficulties, speech and cognitive delays, overgrowth and musculoskeletal anomalies in whom an interstitial duplication of about 400 kb in 4p16.3 was detected by SNP-array analysis. The duplication includes the complete coding sequence of FAM53A, SLBP, TMEM129 and TACC3 genes and the first exon of the FGFR3 gene. Phenotypic comparison with previously described patients harboring a microduplication of similar size and position contributes to better define the clinical correlation of 4p16.3 microduplications, suggesting the existence of a novel distinct and phenotypically recognizable syndrome. In addition, being the duplication identified in our case the smallest so far reported, it allowed us to refine the smallest region of overlap among patients to 222 kb, enabling a more accurate genotype-phenotype correlation for 4p16.3 microduplications.

Conclusions: Our case report provide clinical and molecular evidences supporting the existence of a novel 4p16.3 microduplication syndrome. The genes FAM53A, TACC3 and FGFR3 seems to play a key role in the etiology of the clinical phenotype. Interestingly, our patient is the oldest described so far and for this reason useful to delineate the long-term prognosis of these patients.