A Very Rare Partial Trisomy Syndrome: De Novo Duplication of 16q12.1q23.3 in a Turkish Girl with Developmental Delay and Facial Dysmorphic Features

Array-Based Comparative Genomic Hybridization Analysis in Children with Developmental Delay/Intellectual Disability

Developmental delay (DD) is a condition wherein developmental milestones and learning skills do not occur at the expected age range for patients under 5 years of age. Intellectual disability (ID) is characterized by limited or insufficient development of mental abilities, including intellectual functioning impairments, such as learning and cause–effect relationships. Isolated and syndromic DD/ID cases show extreme genetic heterogeneity. Array-based comparative genomic hybridization aCGH) can detect copy number variations (CNVs) on the whole genome at higher resolution than conventional cytogenetic methods. The diagnostic yield of aCGH was 15.0–20.0% in DD/ID cases. The aim of this study was to discuss the clinical findings and aCGH analysis results of isolated and syndromic DD/ID cases in the context of genotype-phenotype correlation. The study included 139 cases (77 females, 62 males). Data analysis revealed 38 different CNVs in 35 cases. In this study, 19 cases with pathogenic CNVs (13.6%) and five cases with likely pathogenic CNVs (3.5%) were found in a total of 139 cases diagnosed with DD/ID. When all pathogenic and likely pathogenic cases were evaluated, the diagnosis rate was 17.1%. The use of aCGH analysis as a first-tier test in DD/ID cases contributes significantly to the diagnosis rates and enables the detection of rare microdeletion/microduplication syndromes. The clear determination of genetic etiology contributes to the literature in terms of genotype-phenotype correlation.

Clinical Features of de novo Pure 16q21q24.1 Chromosome Duplication

Pure partial duplications of the long arm of chromosome 16 are rare and few cases are described with delineation by chromosomal microarray. Data about clinical abnormalities of pure partial 16q duplications are incomplete because many individuals die during the perinatal period. We describe the clinical features of a 47-month-old Brazilian girl with 16q21q24.1 duplication. To the best of our knowledge, she is the first person with this specific chromosome segment duplication, and we compare her phenotype with the only reported individual alive with intermediate-distal pure 16q duplication.

A rare description of pure partial trisomy of 16q12.2q24.3 and review of the literature

Trisomy 16 is the most common autosomal trisomy in humans, which is almost uniformly embryonic lethal. Partial trisomy 16 including a segment of the long arm of chromosome 16 is occasionally compatible with life and has been associated with severe congenital defects, growth retardation, and early lethality. Segmental trisomy of 16q is usually described concomitantly with partial monosomy of another chromosome, often resulting from a parental balanced translocation. Pure partial chromosome 16q trisomy is exceedingly rare. About nine children with 16q12→qter and 16q13→qter duplication have been reported in the literature, almost all described with monosomy of a second chromosome, and highlighting very few long-term survivors. A single individual with pure partial distal 16q12.1q23.3 duplication has been reported in an infant, underscoring complexities of genetic counseling and management, especially in view of life-limiting congenital anomalies in rare survivors. Here, we present a 12-month-old child with pure 16q12.2q24.3 trisomy, having continued morbidity related to pulmonary hypertension and chronic lung disease. The features of intrauterine growth retardation, facial dysmorphism, hypotonia, congenital heart defect, distal contractures, urogenital abnormalities, and hearing loss support the association with 16q partial trisomy, as in previous studies. This report expands our current understanding related to the survival of infants with large segmental aneusomy of the long arm of chromosome 16.