[Genotypic and phenotypic analysis of a patient with de novo partial monosomy 18p and partial trisomy 18q].

Objective: To explore the genetic cause for a patient with intellectual disability, short stature and multiple congenital anomalies, and to correlate the result with the clinical phenotype.

Methods: Routine karyotyping analysis was carried out on GTG-banded metaphase chromosomes. Single nucleotide polymorphism (SNP) microarray was used to detect microdeletions or microduplications in the patient. Fluorescence in situ hybridization (FISH) was used to ascertain the origin of aberrant chromosomes.

Results: The karyotype of the patient was 46,XY,der(18), while both of his parents had a normal karyotype. SNP array identified a 1.23 Mb deletion at 18p11.32-pter (chr18: 136 227-1 370 501, hg19) and a 33.76 Mb duplication at 18q21.1-qter (chr18: 44 250 359-78 013 728, hg19) in the patient. Above finding was confirmed by dual-color FISH with one color for 18p and another for 18q. The patient presented with some common features of 18p deletion and 18q duplication including intellectual disability and growth retardation, in addition with some features of 18p deletion including pectus excavatum, short stature and growth hormone (GH) deficiency. The patient showed progressive improvement of stature with GH therapy. Comparison of patients with previously reported dup(18q)+del(18p) recombinations suggested that, even for patients with similar breakpoints, their phenotypes have ranged from normal to severe and there were no consistent findings.

Conclusion: As aberrations involving double chromosomal segments often result in phenotypic variability, it has been difficult to correlate the genotype of our patient with his phenotype.