Concurrent pulmonary candidiasis and tuberculosis in type 2 diabetes mellitus: immune pathogenesis and...

Type 2 diabetes mellitus predisposes to opportunistic pulmonary infections. We report sequential invasive pulmonary candidiasis followed by tuberculoma in a patient with newly diagnosed type 2 diabetes mellitus and summarize diagnostic pitfalls and management lessons.

A 67-year-old Han Chinese man with no previously known diabetes presented with cough and severe hyperglycemia (random glucose 36.3 mmol/L; HbA1c 12.7%). Initial chest computed tomography showed right‑upper‑lobe consolidation. Bronchoalveolar lavage metagenomic next‑generation sequencing detected abundant Candida albicans and sputum Gram stain showed Gram‑negative bacteria predominance; sputum culture yielded no definite pathogen, blood cultures were negative, and human immunodeficiency virus test was negative. After intravenous then oral fluconazole plus intensive insulin therapy, the consolidation regressed. Suspected secondary organizing pneumonia was treated with tapering methylprednisolone. One month later, a new 1.5 cm × 1.3 cm solid nodule appeared in the prior lesion bed. computed tomography‑guided biopsy revealed necrosis, and tissue metagenomic next-generation sequencing confirmed Mycobacterium tuberculosis; standard anti‑tuberculosis therapy was initiated.

In patients with diabetes and pulmonary lesions, concomitant or sequential fungal and tuberculous infections should be actively sought with stepwise microbiology (including bronchoalveolar lavage and tissue‑based methods) and early molecular testing (metagenomic next-generation sequencing/Xpert). Steroid exposure for organizing pneumonia may worsen or unmask tuberculosis and must be weighed against infectious risk. Multidisciplinary care (endocrinology-pulmonology-infectious diseases) and rigorous glucose control are essential.