Molecular detection of Tropheryma whipplei DNA: a crucial tool for diagnosing Whipple's disease in the brain. Illustrative case.

backgroundWhipple's disease is a rare chronic infectious disorder caused by the bacterium Tropheryma whipplei. It commonly involves the small intestine and presents with chronic diarrhea, abdominal pain, weight loss, enlarged lymph nodes, and migratory polyarthralgia, with involvement of the CNS. OBSERVATIONS: The authors describe the case of a 69-year-old male who presented with arthritis on immunomodulatory treatment, weight loss, confusion, worsening memory, and right-sided weakness. MRI of the brain revealed a 2.4-cm enhancing mass in the left lentiform nucleus. A stereotactic biopsy was performed, with pathology demonstrating granulomatous inflammation with reactive astrocytes. Broad-range polymerase chain reaction and next-generation sequencing of the tissue detected T. whipplei DNA. Intravenous ceftriaxone yielded no clinical improvement. LESSONS: Whipple's disease should be considered in an immunosuppressed patient presenting with progressive cognitive decline, weight loss, and imaging findings that are atypical for a neoplasm. Whipple's disease can be diagnosed by histological identification of the organism or by the presence of foamy macrophages containing gram-positive bacilli in the biopsy of the small intestine or affected tissues. Its diagnosis can be challenging as T. whipplei grows inconsistently in culture and can rapidly become undetectable with antibiotic therapy. Molecular detection might be required to improve diagnostic accuracy. https://thejns.org/doi/10.3171/CASE24687.