Original ArticlesDiverse clinical outcome of Hunter syndrome in patients with chromosomal aberration encompassing entire and partial IDS deletions: what is important for early diagnosis and counseling?Jezela-Stanek, Aleksandraa; Pokora, Paulinab; Młynek, Marlenac; Smyk, Martad; Ziemkiewicz, Kamilad; Różdżyńska-Świątkowska, Agnieszkae; Tylki-Szymańska, AnnabAuthor Information aDepartment of Genetics and Clinical Immunology, National Institute of Tuberculosis and Lung Disease bDepartment of Paediatric, Nutrition and Metabolic Diseases, The Children’s Memorial Health Institute cDepartment of Medical Genetics, The Children’s Memorial Health Institute dDepartment of Medical Genetics, Institute of Mother and Child eAnthropology Laboratory, The Children’s Memorial Health Institute, Warsaw, Poland Received 9 September 2019 Accepted 26 May 2020 Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website, http://www.clindysmorphol.com. Correspondence to Anna Tylki-Szymańska, Department of Paediatric, Nutrition and Metabolic Diseases, The Children’s Memorial Health Institute, Al. Dzieci Polskich 20, 04-730 Warsaw, Poland, Tel: +48228157584; fax : +48228157489; e-mail: [email protected]; [email protected] Clinical Dysmorphology: April 2021 - Volume 30 - Issue 2 - p 76-82 doi: 10.1097/MCD.0000000000000344 Buy SDC Metrics Abstract Our study aims to delineate the syndromology of Hunter syndrome (MPSII), by presenting three patients with different clinical courses, caused by different genetic mechanisms. Single-nucleotide variants (SNV) or small deletions encompassing the iduronate-2-sulfatase (IDS) gene are identified in the majority of affected individuals, while deletion of contiguous genes or whole IDS gene (described herein) has been reported rarely, mainly in patients with a severe Hunter syndrome presentation. There is; however, lack of reliable genotype–phenotype correlation, especially regarding anthropometric parameters, and thus our understanding of MPSII pathophysiology is not complete. On the basis of our observations, we would like to draw attention to the fact that neurological manifestations observed in patients with contiguous gene deletions, encompassing the IDS gene, may significantly differ from those observed in SNV. The phenotype is; however, difficult to predict and depends on the type (deletion/duplication), size (small/large) of aberration, and gene content. Moreover, it also has implications for genetic counseling, and recurrence risk in those families differs from the usual situation and must be clarified by parental chromosomal studies. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.