Case Report Mendelian Susceptibility to Mycobacterial Disease: The First Case of a Diagnosed Adult Patient in the Czech Republic Miroslav Prucha , 1 Hana Grombirikova , 2,3 Pavel Zdrahal , 4 Marketa Bloomfield , 5,6 Zuzana Parackova , 5 and Tomas Freiberger 2,3 1 Department of Clinical Biochemistry, Hematology and Immunology, Na Homolce Hospital, Prague, Czech Republic 2 Centre for Cardiovascular Surgery and Transplantation, Brno, Czech Republic 3 Medical Faculty, Masaryk University, Brno, Czech Republic 4 Department of Vascular Surgery, Na Homolce Hospital, Prague, Czech Republic 5 Department of Immunology, Motol University Hospital and Second Faculty of Medicine, Charles University, Prague, Czech Republic 6 Department of Pediatrics, omayer’s Hospital and First Faculty of Medicine, Charles University, Prague, Czech Republic Correspondence should be addressed to Miroslav Prucha; miroslav.prucha@homolka.cz Received 13 July 2020; Revised 9 October 2020; Accepted 10 December 2020; Published 21 December 2020 Academic Editor: Christian Drouet Copyright © 2020 Miroslav Prucha et al. is 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. We present a case of a 42-year-old woman with Mendelian susceptibility to mycobacterial disease. e disease was diagnosed at an adult age with relatively typical clinical manifestations; the skeleton, joints, and soft tissues were affected by nontuberculous mycobacteria: Mycobacterium lentiflavum, M. kansasii, and M. avium. A previously published loss-of-function and functionally validated variant NM_000416.2:c.819_822delTAAT in IFNGR1 in a heterozygous state was detected using whole-exome se- quencing. After interferon-c therapy was started at a dose of 200 µg/m 2 three times a week, there was significant clinical im- provement, with the need to continue the macrolide-based combination regimen. In the last 4 months, she has been in this therapy without the need for antibiotic treatment. 1. Introduction Mendelian susceptibility to mycobacterial diseases (MSMD) belongs to the group of primary immunodefi- ciencies, i.e., a: defects in intrinsic and innate immunity. b: MSMD and viral infection: VI-IUIS update [1]. It is a primary immunodeficiency denoted by molecular defects in the interleukin 12 (IL-12)/interferon c- (IFN-c-) de- pendent signalling pathway. e genetic aetiology of the disease was first demonstrated in 1996 [2], and we currently know of variants in 15 genes that, due to allelic hetero- geneity, are the cause of 21 forms of the disease [3, 4]. Patients with this primary immunodeficiency are charac- terized by a narrow vulnerability to poorly virulent mycobacteria, such as bacillus Calmette–Gu´ erin (BCG) vaccines and environmental mycobacteria (EM) [5, 6]. IFN-c is a key player in driving anti-infectious immunity. It is capable of enhancing antigen processing, inducing an antiviral state, and boosting antimicrobial functions. Severe recurrent infections, either disseminated or localized, are typical here [7]. 2. Case Report A 42-year-old female with a suspicion of “immunodefi- ciency” came to the immunology clinic. e reason at the time was a present active infection by atypical mycobacteria that affected the skeleton with multiple defects of the spine ( and L vertebrae), skin, and subcutis of the face, lymph nodes, knee joints, calva, paranasal sinuses, and nose. Hindawi Case Reports in Immunology Volume 2020, Article ID 8836685, 5 pages https://doi.org/10.1155/2020/8836685