Research Article Human Ace D/I Polymorphism Could Affect the Clinicobiological Course of COVID-19 Elifcan Aladag , 1 Zahit Tas , 2 Bilgesu Safak Ozdemir , 3 Tayfun Hilmi Akbaba , 3 Meltem Gulsun Akpınar , 4 Hakan Goker , 1 Tugce Unalan-Altintop , 5 Ahmet Cagkan Inkaya , 2 Alpaslan Alp , 5 Gokhan Metan , 2 Ibrahim Celalettin Haznedaroglu , 1 Banu Balci-Peynircioglu , 3 and Nilgun Sayinalp 1 1 Department of Hematology, Hacettepe University Faculty of Medicine, Ankara, Turkey 2 Department of Infectious Diseases, Hacettepe University Faculty of Medicine, Ankara, Turkey 3 Department of Medical Biology and Genetics, Hacettepe University Faculty of Medicine, Ankara, Turkey 4 Department of Radiology, Hacettepe University Faculty of Medicine, Ankara, Turkey 5 Department of Microbiology and Clinical Microbiology, Hacettepe University Faculty of Medicine, Ankara, Turkey Correspondence should be addressed to Elifcan Aladag; emanuscript.a@gmail.com and Nilgun Sayinalp; nsayinal@gmail.com Received 16 May 2021; Revised 4 July 2021; Accepted 20 August 2021; Published 17 September 2021 Academic Editor: Vijaya Anand Copyright © 2021 Elifcan Aladag et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Introduction. The coronavirus disease 2019 (COVID-19), that is caused by severe acute respiratory syndrome corona virus 2 (SARS-CoV-2), has spread rapidly worldwide since December 2019. The SARS-CoV-2 virus has a great affinity for the angiotensin-converting enzyme-2 (ACE-2) receptor, which is an essential element of the renin-angiotensin system (RAS). This study is aimed at assessing the impact of the angiotensin-converting enzyme (ACE) gene insertion (I)/deletion (D) polymorphisms, on the susceptibility and clinical outcomes of the COVID-19 immunoinflammatory syndrome. Patients and Methods. A total of 112 patients diagnosed with COVID-19 between 1 and 15 May 2020 were enrolled in the study. ACE gene allele frequencies were compared to the previously reported Turkish population comprised of 300 people. Results. The most common genotype in the patients and control group was DI with 53% and II with 42%, respectively. The difference in the presence of the D allele between the patient and control groups was statistically significant (67% vs. 42%, respectively, p < 0:0001). Severe pneumonia was observed more in patients with DI allele (31%) than DD (8%) and II (0%) (p =0:021). The mortality rate, time to defervescence, and the hospitalization duration were not different between the genotype groups. Conclusion. Genotype DI of ACE I/D polymorphism is associated with the infectious rate particularly severe pneumonia in this study conducted in the Turkish population. Therefore, ACE D/I polymorphism could affect the clinical course of COVID-19. 1. Introduction Severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2) is a novel coronavirus subtype from the Sarbecovirus virus family, causing the currently expanding coronavirus disease 2019 (COVID-19) pandemic [1]. As previously dem- onstrated with severe acute respiratory syndrome coronavi- rus, this virus also has a high-affinity potential for the human angiotensin-converting enzyme-2 (ACE-2) [2]. The virus adheres to the nasopharyngeal and alveolar surfaces expressing ACE-2 through the spike proteins located at the viral envelope [3]. The tissue-based renin-angiotensin system (RAS) plays an essential role in the pathobiology of COVID- 19 [4, 5]. While the angiotensin-converting enzyme-1 (ACE- 1) enzyme mediates the formation of angiotensin-2, ACE-2 converts angiotensin-2 to angiotensin-1 by hydrolyzing. That balance is crucial for the genesis of the syndrome, since the imbalance in favor of the angiotensin-2 is implicated in the mechanism exacerbating COVID-19 such as vasoconstric- tion, fibrosis, inflammation, and thrombosis [6]. Hence, Hindawi Journal of the Renin-Angiotensin-Aldosterone System Volume 2021, Article ID 5509280, 7 pages https://doi.org/10.1155/2021/5509280