A case of pulmonary nodular lesion caused by Tropheryma whipplei infection: a case report and literature review.

[BACKGROUND] Tropheryma whipplei is a Gram-positive aerobic bacillus belonging to the phylum Actinobacteria. It is the causative agent of Whipple's disease, a multi-systemic illness that can lead to pneumonia when the lungs are involved. Currently, there is no expert consensus regarding diagnostic criteria for T. whipplei pneumonia. Its clinical manifestations and imaging features lack specificity, often resulting in misdiagnosis or missed diagnosis.

[CASE PRESENTATION] A 69-year-old male presented with intermittent right-sided chest pain and coughing with expectoration. Initial chest imaging suggested a high probability of a malignant lung tumor. Following comprehensive examinations and treatments, the tumor diagnosis was excluded, and an infectious lesion was confirmed. Positron Emission Tomography/Computed Tomography (PET/CT) revealed a marked increase in F-fluorodeoxyglucose (F-FDG) metabolism within the pulmonary lesion. This lesion obstructed the bronchial opening in the outer basal segment of the right lower lobe (RB9) of the lung. Bronchial mucosal biopsy specimens were obtained from this site using biopsy forceps, while lung lesion tissue samples were collected via endobronchial ultrasound (EBUS). Bronchoalveolar lavage fluid (BALF) was subsequently collected at the puncture site and subjected to targeted next-generation sequencing (tNGS), resulting in the detection of T. whipplei. Pathological examination of both biopsy tissues found no evidence of tumor cells. Furthermore, the tuberculosis bacillus infection was ruled out through pathogen testing. After 6 months of anti-infection treatment for T. whipplei, the original lung nodules had significantly shrunk and subsequently disappeared. We conducted a literature review of case reports with relatively complete data, summarizing and analyzing the clinical features, chest imaging manifestations, and diagnostic methods relating to lung infections caused by T. whipplei.

[CONCLUSIONS] The symptoms of T. whipplei infection involving the lungs are indeed nonspecific, and pulmonary nodules are perhaps its most common imaging manifestation. The tNGS has improved the efficiency of pathogenic microorganism diagnosis. Where feasible, tNGS testing should be promptly implemented to avoid misdiagnosis or missed diagnosis. PET/CT can be used as a potential auxiliary diagnostic tool for pulmonary nodules associated with T. whipplei infection.