Forgotten Infection Friday — Nocardia: The Weakly Acid‑Fast Impostor

A 62-year-old man with poorly controlled diabetes presented with weeks of cough, weight loss, night sweats, and cavitary lung lesions initially suspected to be tuberculosis or malignancy. Sputum TB tests were negative and symptoms progressed. Bronchoscopic lung biopsy showed branching gram‑positive filaments that were weakly acid‑fast, consistent with Nocardia species. Nocardia commonly infects immunocompromised hosts, can disseminate to the brain, and is often mistaken for TB, fungal infection, or cancer. Diagnosis relies on modified acid‑fast stain, prolonged cultures, or molecular testing. Treatment requires prolonged antibiotic therapy (commonly TMP‑SMX), sometimes IV agents for severe disease, and early recognition in diabetic or immunosuppressed patients is critical to prevent dissemination.