Ring Chromosome 9 and Chromosome 9p Deletion Syndrome in a Patient Associated with Developmental Delay: A Case Report and Review of the Literature

Ring chromosomes have been described for all human chromosomes and are typically associated with physical and/or mental abnormalities resulting from a deletion of the terminal ends of both chromosome arms. This report describes the presence of a ring chromosome 9 in a 2-year-old male child associated with developmental delay. The proband manifested a severe phenotype comprising facial dysmorphism, congenital heart defects, and seizures. The child also exhibited multiple cell lines with mosaic patterns of double rings, a dicentric ring and loss of the ring associated with mitotic instability and dynamic tissue-specific mosaicism. His karyotype was 46,XY,r(9)(p22q34)[89]/46,XY,dic r(9; 9)(p22q34;p22q34)[6]/45, XY,-9[4]/47,XY,r(9),+r(9)[1]. However, the karyotypes of his parents and elder brother were normal. FISH using mBAND probe and subtelomeric probes specific for p and q arms for chromosome 9 showed no deletion in any of the regions. Chromosomal microarray analysis led to the identification of a heterozygous deletion of 15.7 Mb from 9p22.3 to 9p24.3. The probable role of the deleted genes in the manifestation of the phenotype of the proband is discussed.