Microscopic polyangiitis With Pauci-Immune Glomerulonephritis Associated With Gastrointestinal Tuberculosis

Introduction: Tuberculosis (TB) is a prevalent disease in Guatemala, present in 20-25 cases per 100 thousand inhabitants. Extrapulmonary TB (EPTB) accounts for only 10%-17% of TB cases. The diagnosis of EPTB is challenging, especially in low-resource settings, because TB can present with clinical characteristics of rheumatological, oncological, or other infectious diseases. Occasionally, mycobacterial infection stimulates the immune system, inducing the generation of antibodies that may lead to autoimmune diseases secondary to primary TB infection, such as vasculitis. To the best of our knowledge, no data have been reported on the prevalence of vasculitis, although some studies worldwide have determined that small-vessel vasculitis is the most common. Here, we present a case report of a male patient with EPTB diagnosed with Microscopic polyangiitis (MPA). Methods: A 17-year-old boy with no past medical history visited the emergency room with a three-day history of gastrointestinal bleeding. During hospitalization, acute kidney injury (AKI), disseminated lymphadenopathy, imaging studies, renal biopsy, and immunological tests were performed to confirm the diagnosis. Results: Endoscopy revealed a duodenal lesion containing Mycobacterium TB DNA. Further investigation of AKI led to autoimmune serological tests and kidney biopsy, confirming the diagnosis of antineutrophil cytoplasmic antibodies (ANCA)-positive pauci-immune GN. The patient was treated with antituberculous agents, steroids, and plasmapheresis. However, he developed alveolar hemorrhage and respiratory failure leading to death. Conclusion: TB is a common disease in low-income countries, with the pulmonary form being the most common presentation; however, the bacteria can spread to any organ, known as EPTB. It is important to consider that the inflammatory reaction associated with any form of TB can generate other types of noninfectious inflammatory diseases, such as ANCA-positive pauci-immune GN.