Tetrasomy 18p Syndrome: A Rare Case with Congenital Hypoplasia of the Depressor Angularis Oris

Published date: Dec 31 2025

Journal Title: Dubai Medical Journal

Issue title: Dubai Medical Journal (DMJ): Volume 8, Issue 4

Pages: 469-475

DOI: 10.18502/dmj.v8i4.20486

Anwar Khanahkhan@dubaihealth.aeNeonatology Department Dubai Hospital, Dubai Health, Dubai

Khalid IqbalNeonatology Department Dubai Hospital, Dubai Health, Dubai

Mahmoud JalalNeonatology Department Dubai Hospital, Dubai Health, Dubai

Juhi HussainNeonatology Department Dubai Hospital, Dubai Health, Dubai

Waseem KhanNeonatology Department Dubai Hospital, Dubai Health, Dubai

Mostafa Abdel Rauf Mahmoud El BolkoniNeonatology Department Dubai Hospital, Dubai Health, Dubai

Introduction: Tetrasomy 18p syndrome is an extremely rare chromosomal disorder where there are four copies of chromosome 18 instead of two due to the presence of isochromosome 18p. We aim to report a case of tetrasomy 18p with unusual phenotypic presentation with congenital hypoplasia of depressor angularis oris muscle.

Case Report: We present a case of a neonatal boy with tetrasomy 18p syndrome, who was initially admitted for bilateral undescended testes. This syndrome has been found to have variability in its clinical features. The patient was found to have soft dysmorphic features, feeding difficulty, congenital hypoplasia of the depressor angularis oris muscle, growth retardation, hypotonia, and jaundice. During follow-up, he was found to have strabismus, hearing loss, failure to thrive, and global developmental delay.

Conclusion: We compared the phenotypic characteristics of our case with previously reported cases of this syndrome. To the best of our knowledge, congenital hypoplasia of the depressor angularis oris has not been reported previously as a phenotypic characteristic of this syndrome and might be considered a diagnostic feature if more cases are reported in the future. Additionally, it is easy to miss such cases, as some neonates do not present with typical dysmorphic features that would prompt a karyotype analysis.

Keywords: tetrasomy 18p, isochromosome, dysmorphic, chromosome, syndrome, depressor angularis oris

[1] Wei J, Xie Y, He W, Liu W, Jian W, Chen M, et al. Clinical outcome: A monosomy 18p is better than a tetrasomy 18p. Cytogenet Genome Res. 2014;144(4):294–298.

[2] Plaiasu V, Ochiana D, Motei G, Georgescu A. A rare chromosomal disorder - isochromosome 18p syndrome. Maedica (Bucur). 2011;6(2):132–136.

[3] Abeliovich D, Dagan J, Levy A, Steinberg A, Zlotogora J. Isochromosome 18p in a mother and her child. Am J Med Genet. 1993;46(4):392–393.

[4] Boyle J, Sangha K, Dill F, Robinson WP, Yong SL. Grandmaternal origin of an isochromosome 18p present in two maternal half-sisters. Am J Med Genet. 2001;101(1):65–69.

[5] Takeda K, Okamura T, Hasegawa T. Sibs with tetrasomy 18p born to a mother with trisomy 18p. J Med Genet. 1989;26(3):195–197.

[6] Sebold C, Roeder E, Zimmerman M, Soileau B, Heard P, Carter E, et al. Tetrasomy 18p: Report of the molecular and clinical findings of 43 individuals. Am J Med Genet A. 2010;152A(9):2164–2172.

[7] Zavala J, Ramirez M, Medina R, Heard P, Carter E, Crandall A, et al. Psychiatric syndromes in individuals with chromosome 18 abnormalities. Am J Med Genet B Neuropsychiatr Genet. 2010;153B(3):837–845.

[8] O’Donnell L, Soileau BT, Sebold C, Gelfond J, Hale DE, Cody JD. Tetrasomy 18p: Report of cognitive and behavioral characteristics. Am J Med Genet A. 2015;167(7):1474–1482.

[9] Bawazeer S, Alshalan M, Alkhaldi A, AlAtwi N, AlBalwi M, Alswaid A, et al. Tetrasomy 18p: Case report and review of literature. Appl Clin Genet. 2018;11:9–14.