Background: Talaromyces marneffei  is considered to commonly cause infection in individuals with human immunodeficiency virus (HIV) infection. However, the epidemiology of T. marneffei  has changed, and an increasing number of HIV-negative but immunodeficient patients are infected with T. marneffei . The mechanisms of T. marneffei  infection of HIV-negative hosts are complex and diverse. We report 2 cases of HIV-negative lung cancer with T. marneffei  infection and positive anti-interferon-gamma autoantibodies (AIGAs) to provide clinical experience.
Case Presentation: We report lung adenocarcinoma combined with T. marneffei  infection in HIV-negative patients, and their AIGAs were measured. Both patients were male with a family history of cancer and presented with recurrent fever and cough. The patients were negative for HIV antibodies but positive for AIGAs. Chest computed tomography (CT) showed pulmonary nodules, exudative lesions and solid changes. The patients were diagnosed with lung adenocarcinoma and Talaromycosis marneffei  (TSM) by pathological examination and tissue culture. Patient 1 received only antifungal treatment, refused antitumor treatment and died in February 2019, and Patient 2 unfortunately died in April 2019 after antifungal and antitumor treatments.
Conclusion: An increasing number of HIV-negative but immunodeficient patients are infected with T. marneffei . The 2 patients in this report had lung cancer and positive AIGAs, causing immunodeficiencies, but the mechanism of T. marneffei  infection in such patients is complex. Clinically, we should consider a comprehensive immunological examination to avoid the omission of other immunodeficiencies. We recommend routine testing for AIGA levels in HIV-negative marneffei patients. It is difficult to distinguish between lung cancer and disseminated TSM due to similar clinical characteristics and imaging, and multiple biopsies and cultures of diseased tissue are necessary. Early antifungal treatment and standard antitumor treatment can achieve satisfactory curative effects when a patient has both diseases.
Keywords: Talaromyces marneffei , lung adenocarcinoma, adult immunodeficiency, anti-interferon-γ antibodies