Shi HJ, et al. J Korean Med Sci. 2023 Jun;38(28):e217. https://doi.org/10.3346/jkms.2023.38.e217

Pneumocystis jirovecii pneumonia (PJP) is a rare opportunistic infection in patients with solid malignancies. This study aimed to examine the characteristics of patients with solid cancers and PJP. We retrospectively reviewed the medical records of patients with solid tumors and PJP over an 11-year period, enrolling a total of 47 patients (30-day survival group: n = 20, 30-day mortality group: n = 27). Only 34% of patients received ≥20 mg of prednisolone for ≥2 weeks, and the 30-day mortality rate was 57.4%. The 30-day survival group included more women and patients with colon cancer than the mortality group. Furthermore, absolute lymphocyte counts (ALCs) were decreased at PJP symptom onset, as compared with the values observed 1–3 months earlier. Increased oxygen demand and low ALCs after 5–7 days of PJP treatment were also related to poor prognosis. Due to the limitations of this retrospective study, further studies that adhere to the PJP criteria of the European Organization for Research and Treatment of Cancer and the Mycoses Study Group Education and Research Consortium will be needed to evaluate PJP in solid malignancies more clearly.

Background/Objectives: The incidence of nontuberculous mycobacterial (NTM) infections has increased globally; however, the clinical manifestations and optimal treatment strategies for extrapulmonary NTM infections remain poorly defined. This study assessed the clinical manifestations and treatment outcomes of extrapulmonary NTM infections. Methods: Data from adult patients with suspected extrapulmonary NTM infections at a tertiary-care hospital from 2009–2022 were categorized into NTM disease and isolation groups. Diagnosis of NTM disease relied on stringent criteria, whereas isolation required NTM isolation without meeting the criteria for infection. Results: Among 75 patients evaluated, 32 (42%) were diagnosed with NTM disease and 43 (57%) with NTM isolation. History of immunosuppressant use within the past 3 months (p = 0.070) and injection (p = 0.001) were more frequent in the disease group. The median interval from symptom onset to evaluation was 106.6 and 20 days in the disease and isolation groups, respectively. The prevalence of positive NTM polymerase chain reaction results (36.4%, p = 0.003) and acid-fast bacillus staining (39.1%, p < 0.001) was significantly higher in the disease group than in the isolation group. Mycobacterium intracellulare (21.9%), M. abscessus (15.6%), M. chelonae (9.4%), and M. fortuitum complex (9.4%) were the most frequently identified species. Of the 27 patients in the disease group who received treatment, 13 improved, four experienced treatment failure, seven were lost to follow-up, and three died during treatment, with one death directly attributable to NTM disease. Conclusions: NTM disease exhibits a spectrum of clinical manifestations. Accurate diagnosis is crucial for initiating effective treatment.

Kim S, et al. Infect Chemother. 2023 Aug;55:e34. https://doi.org/10.3947/ic.2023.0032

Musculoskeletal infections caused by nontuberculous mycobacteria (NTM) can clinically and radiologically mimic malignant disorders. Accurate diagnosis requires correlation between microbiological, histopathological, and clinical findings. We report a case of diffuse large B-cell lymphoma (DLBCL) initially misdiagnosed as NTM infection based on polymerase chain reaction (PCR) positivity despite negative cultures. A 58-year-old man with diabetes mellitus and prior coronary artery bypass grafting presented with a progressively enlarging painful right flank mass. Magnetic resonance imaging (MRI) showed an infiltrative lesion involving multiple abdominal wall muscles and extension to the L2 vertebral body. Initial bone and soft tissue biopsies revealed chronic inflammation with necrosis. NTM PCR was positive; however, acid-fast bacillus (AFB) staining and culture were negative. Empirical antimycobacterial therapy was initiated.After three months, the lesion progressed, and repeat biopsy confirmed Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoma, stage IV. The patient received six cycles of R-CHOP chemotherapy with an initial metabolic response on 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), followed by early relapse despite salvage chemotherapy and palliative radiotherapy. He ultimately died of refractory lymphoma. This case underscores the importance of re-evaluating suspected NTM infection with negative cultures when the clinical course is atypical or unresponsive to therapy. PCR positivity alone, in the absence of microbiological culture confirmation and compatible clinicopathological findings, should not be considered sufficient to establish a diagnosis of NTM infection. Diagnostic anchoring to molecular test results without clinicopathological reassessment may lead to critical delays and death.

Background: Scrub typhus is commonly misdiagnosed because of nonspecific clinical features and limited data on the performance of diagnostic tests. This study aimed to evaluate the accuracy of commercially available serological and molecular assays for diagnosing scrub typhus. Methods: Adult patients with suspected scrub typhus who visited a tertiary-care hospital in South Korea from July 2022 to December 2024 were prospectively enrolled. Scrub typhus was confirmed by either a positive real-time polymerase chain reaction (PCR) result for Orientia tsutsugamushi or a ≥ four-fold increase in the O. tsutsugamushi-specific total immunoglobulin (Ig) antibody titer on an immunofluorescence assay (IFA). The diagnostic performances of the serial IFA, an immunochromatography-based rapid diagnostic test (ICT), and multiplex real-time PCR targeting the groEL and 47-kDa genes were compared. Results: Among 159 patients, 81 had scrub typhus and 78 did not. The sensitivity and specificity were 64% and 100% for the serial IFA, 75% and 91% for the ICT, and 95% and 100% for multiplex PCR, respectively. The area under the curve was significantly higher for the ICT (0.819) than for the acute-phase IFA (0.743, p = 0.02). Conclusions: Multiplex real-time PCR provided rapid and highly accurate confirmation of scrub typhus, and an acute-phase ICT may be an alternative to a single acute-phase IFA for early clinical decision-making.