Acute Respiratory Failure due to Pulmonary Toxoplasmosis in an Immunocompetent Patient: A Case Report.

Pulmonary toxoplasmosis is a rare but potentially life-threatening manifestation of Toxoplasma gondii infection in immunocompetent individuals. Clinical presentation is often nonspecific and may mimic viral or atypical pneumonia, leading to delayed diagnosis. We report the case of a previously healthy 32-year-old man who presented with a mononucleosis-like syndrome complicated by rapidly progressive hypoxemic respiratory failure requiring invasive mechanical ventilation. Initial evaluation revealed marked systemic inflammation, cytopenias, hyperferritinemia, and mixed-pattern hepatitis. Chest computed tomography demonstrated bilateral consolidations, ground-glass opacities, pleural effusions, and interstitial changes. Extensive microbiological and immunological investigations were initially unrevealing. Polymerase chain reaction (PCR) testing for T. gondii was positive in blood despite negative IgG serology and isolated IgM positivity, raising concern for potentially misleading serological findings. The diagnosis of pulmonary toxoplasmosis was subsequently confirmed by PCR detection of T. gondii DNA in bronchoalveolar lavage fluid. Targeted treatment with trimethoprim-sulfamethoxazole led to rapid clinical and biochemical improvement, allowing successful extubation after 6 days of mechanical ventilation and complete radiological resolution prior to discharge. This case highlights the diagnostic challenges of pulmonary toxoplasmosis in immunocompetent hosts and underscores the importance of molecular testing in critically ill patients with severe pneumonia and ambiguous serological findings.