18p Deletion Syndrome Originating from Rare Unbalanced Whole-Arm Translocation between Chromosomes 13 and 18: A Case Report and Literature Review

Abstract

18p deletion (18p-) syndrome is a rare chromosome abnormality that has a wide range of phenotypes, with short stature, intellectual disability, and facial dysmorphism being the main clinical features. Here, we report the first case in Korea of a 16-year-old male adolescent with 18p- syndrome resulting from de novo unbalanced whole-arm translocation between chromosomes 13 and 18 (45, XY, der(13;18)(q10:q10)). Three rare clinical findings were discovered that had not been reported in the previous literature; morbid obesity without other hormonal disturbances, rib cage deformity leading to the direct compression of the liver, and lumbar spondylolisthesis at the L5-S1 level. This case expands the phenotypic spectrum of 18p- syndrome and highlights the importance of considering chromosomal analysis, since this syndrome can be easily overlooked in a clinical setting, especially without distinctive symptoms of other organs, due to its nonspecific but typical features of short stature and mild intellectual disability with a mildly dysmorphic face. Moreover, since not all cases of 18p- syndrome with unbalanced translocation (13;18) show the same phenotype, multidisciplinary examinations and follow-up seem to be important to monitor evolving and developing clinical manifestations and to predict prognosis in advance associated with the specific genes of 18p breakpoint regions.

Keywords: 18p deletion syndrome; chromosomal aberration; facial dysmorphism; intellectual disability; monosomy 18p; short stature; unbalanced translocation.

Figure 1

Skeletal deformities of the patient. (a) Axial and coronal CT scan sections showing abnormally curved right 8th rib and costal that directly compress the liver (white arrow); (b) sagittal lumbosacral X ray showing spondylolisthesis of L5-S1 (black arrow).

Figure 2

Cytogenetic results. (a) The karyotype of proband: 45, XY, der(13;18) (q10;q10), indicating unbalanced translocation between the long arm of one chromosome 13 and the long arm of one chromosome 18 (white arrow); (b) array-based comparative genomic hybridization (aCGH) of proband revealed as 15 Mb deletion in the short arm from 18p11.32 to p11.21.