Isolated splenic tuberculosis detected only on FDG-PET

Tuberculosis (TB) is a well-known problem in developing countries but has shown resurgence in non-endemic populations in recent years. This may be due to increased migration, and is more commonly seen in populations with lowered immunity due to various causes. Isolated splenic TB is extremely rare, especially in immunocompetent patients. In this case report we have described an immunocompetent female, presenting to the physician with fever, without any chest symptoms or weight loss. All microbiological investigations for pyrexia of unknown origin were done, which did not reveal the cause. Imaging modalities including chest radiographs and ultrasound did not reveal any significant abnormalities. Finally, fluorodeoxyglucose (FDG)-positron emission tomography (PET) showed FDG-avid multiple focal nodular lesions (not seen on contrast and non-contrast CT). MRI including diffusion-weighted imaging did not reveal the splenic nodules. PET-directed CT-guided biopsy of the splenic lesions was performed, with histopathology findings suggestive of TB. Atypical clinical and imaging presentations are not uncommon in TB. History of exposure to TB may not be present. Nevertheless, TB should be kept in mind as a differential diagnosis in patients with fever, and extensive search of the source is important. Splenic TB reported in literature to date has been detected by morphological imaging modalities such as ultrasound or contrast CT. Ours is possibly the first case reported in the English literature where FDG-PET has detected the lesions that other imaging modalities failed to show, thus illustrating the role of molecular imaging in the evaluation of pyrexia of unknown origin to localize the site of affection.