A 65-year-old Asian woman was admitted to our clinic in August 2019 due to fever (38.3-39  C), chest tightness, cough producing sputum, and shortness of breath for one day. Her clinical history could be defined by long-term leukopenia. She was diagnosed with MDS in 2014, after which she received supportive treatments. In 2019, she was admitted to the hospital with increased bone marrow blasts (10% vs 4%) and decreased megakaryocytes with small round separated nuclei (Figure 1A-E, Table 1). She received four courses of amifostine, but her symptoms did not improve. During hospitalization, she was infected with recurrent pneumonia, which could be relieved by multiple antibiotic treatments (Figure 2A and B). She received voriconazole after the last course in July 2019. Two months later, the symptoms of fever and pneumonia re-appeared again (Figure 2C). 
On admission, she presented with fever and chest pain, and blood cell count at that time revealed lymphocytopenia and monocytopenia. The blood routine test showed a white blood cell (WBC) count of 1800 cells/mm3, a low monocyte count of 0-0.1 cells/mm3; a hemoglobin level of 7.6 g/dL; and a platelet count of 17 x 109/L. The absolute count of B cell (CD19+) was 6x106/L (50-670x106), NK cell (CD3-/CD16+56+) count was 34x106/L(40-1000x106/L). The CD4+ T-cell count was 141 cells/mm3 and the CD4/CD8 ratio was 0.99. She also had splenomegaly (4.1 cm in size) and iron overload (ferritin: 2361.4ng/mL). The results of Epstein-Barr virus (EBV)-DNA and cytomegalovirus (CMV)-DNA were negative. Next, the patient was treated with tigecycline, ceftazidime, and voriconazole according to the manifestation of lung computed tomography (CT) scan (Figure 2D). Furthermore, Klebsiella pneumoniae infection was confirmed by sputum culture analysis, after which she received therapy with caspofungin, posaconazole, cefoperazone, linezolid, ganciclovir, sulfamethoxazole, amphotericin B, and polymyxin subsequently. However, no significant improvement was observed with reference to fever and pneumonia. During this time, she developed chest tightness and dyspnea which required continuous high-flow oxygen inhalation. She was not able to undergo a bronchoscopy. Complicated with severe infection, the patient also developed acute heart failure. Eventually, we sequenced the patient's peripheral blood specimens despite her repeated negative sputum culture, after which the M. kansasii infection was confirmed. Consequently, she was given antibiotic therapy, consisting of ethambutol, rifabutin, and clarithromycin as recommended. Her situation significantly improved within 2 weeks of therapy (without fever). C-reactive protein (CRP) level remarkably decreased from 250.87 mg/L to an almost normal level. According to the above-mentioned signs and symptoms, the patient was suspected of having MonoMAC syndrome. The next-generation sequencing (NGS, peripheral blood) found a heterozygous mutation in GATA2 (exon6:c.1126_1128del:p.K376del) along with U2AF1 (exon2:c.C101T:p.S34F), SETBP1 (exon4, cG2602A:pD868N, exon4:cG2608A:pG870S), ASXL1 (exon12:c.G2548T:p.E850X) as well as KMT2D, BRAF, EPPK1, and ETV6. Her son was further confirmed with the same GATA2 mutation with oral mucosal specimen. Unfortunately, the patient died of carbapenem-resistant Klebsiella pneumoniae bloodstream infection on October 2019, 41 days after the MonoMAC diagnosing.
Computed tomography (CT) manifestation of recurrent pulmonary infection. The recurrent pneumonia was observed during the hospitalization.