Case Report: Chronic Q fever mimicking malignancy and tuberculosis in a hemodialysis patient: multidisciplinary diagnosis guided by metagenomic next-generation sequencing.

BACKGROUND: Q fever, caused by Coxiella burnetii, is a rare zoonosis whose clinical presentation is highly heterogeneous. Chronic Q fever can present with atypical systemic masses, creating significant diagnostic challenges as it lacks distinctive imaging features, often leading to misdiagnosis.

CASE PRESENTATION: We report a case of a 50-year-old woman on maintenance hemodialysis who presented with a one-month history of generalized myalgia and abdominal discomfort. Initial PET-CT imaging revealed multiple hypermetabolic abdominal lesions (SUV∼max∼ 7.1), mimicking metastatic malignancy. Histopathology of abdominal biopsies showed granulomatous inflammation with necrosis but lacked definitive microbiological evidence. Empirical anti-tuberculosis therapy was initiated based on clinical suspicion. Despite initial clinical improvement, the patient experienced recurrence of symptoms and radiological progression after 1 year. Re-evaluation with transesophageal echocardiography suggested the possibility of infective endocarditis. Crucially, metagenomic next-generation sequencing (mNGS) of a repeat biopsy identified Coxiella burnetii, confirming chronic Q fever. Targeted doxycycline therapy resulted in sustained clinical and radiological improvement, with lesion resolution confirmed at the 14-month follow-up.

CONCLUSION: This case underscores the diagnostic difficulty of chronic Q fever due to its non-specific presentation and imaging characteristics. PET-CT may suggest malignancy, but incorporating advanced molecular diagnostics such as mNGS is critical for accurate pathogen identification. Recognizing atypical manifestations and utilizing integrative diagnostic approaches can facilitate timely, targeted therapy, improving clinical outcomes in rare infectious diseases like Q fever.