Individuals with various sized terminal duplications of chromosome 5p or terminal deletions of chromosome 18q have been described. These aberrations may cause congenital malformations and intellectual disability of varying severity.
Via an international collaborative effort, we obtained a cytogenetic diagnosis for a 5‐year‐old boy of Afro‐Caribbean ancestry who has global developmental delay, dysmorphology, hypotonia, feeding difficulties, bilateral club feet, and intellectual disability.
Conventional G‐banded karyotyping showed additional chromatin of unknown origin on the long arm of chromosome 18. SNP microarray confirmed the loss of ~6.4 Mb from chromosome 18q: arr[hg19] 18q22.3‐q23(71,518,518‐77,943,115)x1. The source of the additional chromatin was determined from the microarray to be ~32 Mb from the short arm of chromosome 5 (arr[hg19] 5p13.3‐p15.33(51,045‐32,062,984)x3). The unbalanced translocation was verified by fluorescent in situ hybridization (FISH). Both parents are healthy and have normal karyotypes suggesting that this abnormality arose de novo in the proband, although gonadal mosaicism in a parent cannot be excluded.
We describe a 5‐year‐old boy who has global developmental delay, dysmorphology, and multiple congenital abnormalities. Karyotype showed additional chromatin on chromosome 18q. Microarray showed an approximate 32 Mb duplication of material from chromosome 5p (partial trisomy), and an approximate 6.2 Mb deletion from chromosome 18q (partial monosomy). FISH confirmed the unbalanced translocation.