S5419 A Case of Catastrophic Antiphospholipid Syndrome Manifesting as Abdominal Pain

Introduction: Antiphospholipid syndrome (APS) is an autoimmune disorder marked by recurrent venous and arterial thromboses due to antiphospholipid antibodies. Catastrophic APS (CAPS) is a rare, rapidly progressive form characterized by widespread small vessel thrombosis and multiorgan failure. Gastrointestinal (GI) involvement is uncommon but typically includes liver complications such as Budd-Chiari syndrome and hepatic infarction due to hepatic vein thrombosis. Other GI manifestations include mesenteric and splenic infarction and gastric ulcers. We present a case of a 32-year-old man with vague abdominal pain, ultimately diagnosed with early CAPS, highlighting the need for awareness of atypical CAPS presentations involving the GI system. Case Description/Methods: A 32-year-old man with quadruple-positive APS, rheumatoid arthritis, and Gilbert syndrome presented with facial rash, abdominal pain, and vomiting after switching from warfarin to low molecular weight heparin for elective surgery. Initial labs showed mild transaminitis (aspartate aminotransferase [AST] 39 U/L, alanine aminotransferase [ALT] 86 U/L), thrombocytopenia (Platelets 133), and international normalized ratio 1.44. Computed tomography abdomen/pelvis showed splenomegaly and gastric distension without evidence of infarction. Esophagogastroduodenoscopy showed diffuse gastritis and gastric purpura. He developed worsening abdominal pain, fevers, and acute kidney injury. On day 4, imaging showed multiple new hepatic infarcts and splenic lesions. Repeat labs: AST 383 U/L, ALT 927 U/L, platelets 45. He was diagnosed with CAPS and received steroids, plasmapheresis, and anticoagulation with initial improvement. He was transferred to another institution for further CAPS management. On day 9, severe epigastric pain recurred with new multifocal hepatic and splenic infarcts. He was treated with another steroid course, plasmapheresis, and Rituximab, with significant improvement. He was discharged home on prednisone, atovaquone, pantoprazole, warfarin, and vitamin D. Discussion: This is a rare case of CAPS presenting as non-specific abdominal pain following warfarin discontinuation. While gastrointestinal symptoms are rare in APS, they are more common in CAPS, particularly involving the liver and spleen. However, abdominal pain as a primary symptom is rarely reported, especially in adults. This case underscores the need for high clinical suspicion for hepatic and splenic infarction in APS patients with vague abdominal symptoms, especially with subtherapeutic international normalized ratio. It supports early and repeat computed tomography or MRI imaging to aid diagnosis.