Pott’s Disease Masquerading as Musculoskeletal Back Pain: A Lesson in Diagnostic Bias

INTRO:Roughly one-third of the world's population is estimated to be infected with Mycobacterium Tuberculosis (TB), however as its manifestations often mimic more common etiologies it continues to present a diagnostic challenge in non-endemic countries. Spinal Tuberculosis or Pott's Disease is one of the most common extrapulmonary manifestations of TB, however it is rarely on the top of our differential in patients presenting with back pain. Here we report such a case of extra-pulmonary TB that was misdiagnosed as sarcoidosis. CASE:A 42-year-old African American Male with a past medical history of Sarcoidosis and Abdominal Tuberculosis in the 1990's prior to immigrating to the United States from Congo for which he underwent an 8-month course of Rifamycin-based antibiotics who presented to the Emergency Department with a 3-month history of right flank and lower back pain. In the ED, X-rays of the thoracic and lumbar spine were noted to unremarkable with blood work significant for an elevated D-Dimer. On subsequent CT scan to rule out pulmonary embolism (PE) was found to have thoracic adenopathy and pulmonary nodules suggestive of sarcoidosis. Further work-up including bronchoscopy showed violaceous plaques and endobronchial lymph node biopsy yielding nonnecrotizing granulomas with morphology favoring sarcoidosis. Serial AFB stains were noted to be negative and given his work-up for active TB was grossly negative, patient was discharged to with a working diagnosis of sarcoidosis. On follow-up with his PCP, he continued to have recurrent back pain and was started on a short course of steroids and underwent MRI imaging of his spine. Imaging revealed a large multi-loculated mass located to the right of the T10-T12 vertebrae concerning for tuberculous osteomyelitis. He was admitted to Neurosurgery and underwent emergency surgical decompression & evacuation of the abscess. Intraoperative biopsy of the thoracic spine was found contain necrotizing granulomas with (+) AFB stain. Patient was started on anti-TB medications with subsequent improvement in his symptoms. DISCUSSION:The clinical manifestations of extra-pulmonary tuberculosis are often vague and can lead to a delay in definitive therapy. The difficulty in distinguishing disseminated TB from sarcoidosis is challenging, especially when histologic evaluation is suggestive of non-caseating granulomas. In patients with a history of TB infection, physicians should have a high clinical suspicion for extra-pulmonary manifestations of disease and a low threshold for further radiologic evaluation.