Thrombotic Microangiopathy and Venous Thrombosis in a Patient With Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis.

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a systemic pauci-immune small vessel vasculitis. Its various presentations make AAV diagnosis challenging. Here, we present a case of AAV with thrombotic microangiopathy (TMA) and deep venous thrombosis (DVT). An 82-year-old Hispanic woman presented to the emergency department with malaise, lower extremity pain, and oliguria for three days. Her vital signs were normal, and her physical examination was unremarkable. The initial laboratory revealed thrombocytopenia (18 x 10/µL), elevated creatinine (8.35 mg/dL), high lactic acid dehydrogenase (1627.5 U/L), an international normalized ratio of 1.6, and an activated partial thromboplastin time of 49 seconds. Urinalysis showed microscopic hematuria and proteinuria, and peripheral smear revealed schistocytes. She was admitted with concern for TMA. Further workup revealed an antinuclear antibody titer of 1:80, an ADAMTS13 level of 62%, a rheumatoid factor level of 151.7 IU/L, and myeloperoxidase (MPO)-ANCA level of 173 AU/mL. A computed tomography scan of the chest/abdomen/pelvis revealed pulmonary fibrosis and multifocal consolidations. She was also found to have extensive DVT of the lower extremities. Renal biopsy revealed early changes of TMA with one cellular crescent. She was diagnosed with AAV based on the kidney and lung findings, as well as the high titer MPO-ANCA. Her platelet count and creatinine improved significantly following treatment with plasma exchange, steroids, and rituximab. Unfortunately, she was then found to have an acute bowel perforation and expired. Even though typically rare, an increased incidence of venous thromboembolism (VTE) and TMA has been reported in patients with AAV. Its prompt recognition and treatment by clinicians are critical to mitigate the unfavorable outcomes from this condition.