Co-infection With Mycobacterium Tuberculosis Complex and Pneumocystis Jirovecii in a Non-HIV-infected Patient With Interstitial Lung Disease: A Case Report

Abstract Introduction: Co-infection with Pneumocystis jirovecii (PJP) and Mycobacterium tuberculosis complex (MTBC) is rare in HIV-seronegative patients. Because it is associated with unknown morbidity and a high mortality rate especially in patients with immunosuppression. But concurrent infections pose a diagnostic challenge owing to similar clinical features. Data suggests a high prevalence of such concurrent infections in developing countries but limited diagnostic modalities especially in resource constraint setup limits accurate diagnosis. This study reports a rare case of PJP co-infection with MTBC in a relatively immunocompetent patient which presented with uncommon radiological findings. Case presentation: A 84-year-old man (former smoker, 30 pack years) with a newly discovered unclassified interstital lung disease (ILD) and a history of hypertension presented with dyspnea, fever, and dry cough for one month to the hospital. He was treated with glucocorticoid for one week briefly and had been under treatment of antibiotics during his one-month disease course before this admission. HIV testing and immunoglobulin levels were normal in the hospital course. A lung computed tomography (CT) scan revealed mostly emphysema appearance but a few regions look like cysts and ground glass opacity diffused infiltration (Figure 1 A). Antibiotics and corticosteroids were administrated at the beginning. However, the patient experienced recurrent fever and a new epilepsy with the reduction of the glucocorticoid dosage. Sputum mNGS detected Mycobacterium tuberculosis complex and Pneumocystis jiroveci confirmed the diagnosis of co-infection with PJP and MTBC. Standard antituberculosis agents and sulfamethoxazole/trimethoprim and corticosteroids were administrated. After one month follow-up, the patient was in good condition despite of ILD and emphysema in his lung (Figure 1 B). Disscussion: Patients with interval fever on long-term antibiotics and glucocorticoid therapy in areas with a high incidence of Mycobacterium tuberculosis may be co-infected with Pneumocystis jirovecii. When opportunistic infections are suspected, diagnostic procedures including invasive ones should be performed as soon as possible and appropriate interventions need to be carried out promptly. Immunodeficiency patients are susceptible to opportunistic infections. mNGS is valuable for diagnosis and treatment. Although the image of MTBC and PJP infections lack specificity, they exhibit distinctive features.