Acute eosinophilic pneumonia with detection of pure Tropheryma whipplei in bronchoalveolar lavage fluid: a case report

Acute eosinophilic pneumonia (AEP) is a rare but potentially severe respiratory illness. <i>Tropheryma whipplei</i> can also cause acute pulmonary infection, leading to atypical symptoms and computerized tomography (CT) findings. We report a case of acute eosinophilic pneumonia that was misdiagnosed as a <i>Tropheryma whipplei</i> infection based on targeted next-generation sequencing (tNGS) of the bronchoalveolar lavage (BAL) fluid. A 51-year-old male firefighter was admitted with a 7-day history of dry cough and 1 day of fever, initially diagnosed with community-acquired pneumonia and treated empirically with antibiotics. TNGS of BAL fluid identified only <i>Tropheryma whipplei</i>, leading to a misdiagnosis of <i>T. whipplei</i> pneumonia. Despite antibiotic treatment, the patient's condition worsened, and a revised diagnosis of AEP was made based on persistent eosinophilia and pathological findings. Treatment with methylprednisolone led to rapid improvement. The detection of a high sequence count of <i>Tropheryma whipplei</i> as the sole bacterium in patients suspected of having acute eosinophilic pneumonia can hinder the diagnosis and treatment of the patient, highlighting the importance of differential diagnosis and the order of treatment choices.