Case Report: A rare presentation of gastrointestinal amyloidosis: unmasking the hidden culprit of chronic epigastric pain and weight loss

Amyloidosis is a rare, heterogeneous condition characterized by extracellular deposition of misfolded protein fibrils, resulting in organ dysfunction. Gastrointestinal amyloidosis (GIA), an uncommon manifestation, is often underdiagnosed due to its nonspecific symptoms, such as weight loss, abdominal pain, and diarrhea. Early recognition and accurate amyloid typing are crucial, as treatment strategies depend on the specific subtype involved. We report a case of a 42-year-old African male presenting with chronic epigastric pain, significant weight loss (BMI: 17.1), and a history of GERD. He had recently traveled to Equatorial Guinea. His symptoms, including nausea, decreased appetite, constipation, and persistent epigastric pain, were unresponsive to proton pump inhibitors. On examination, he was hypotensive and tachycardic. Laboratory workup revealed hyponatremia and elevated troponin T. Imaging showed fecal impaction and pyloric edema. Upper endoscopy and colonoscopy with biopsies confirmed amyloid deposition in the stomach, duodenum, ileum, and colon. Congo red staining demonstrated classic apple-green birefringence under polarized light. Cardiac evaluation revealed reduced global longitudinal strain. Serum studies showed elevated free lambda light chains and an IgG-lambda monoclonal band, while the urine protein/creatinine ratio was 361 mg/g, consistent with proteinuria. Chronic hepatitis B infection with detectable HBV DNA and elevated gamma/delta T cells on the lymphoma panel raised concerns for an underlying T-cell lymphoproliferative disorder. This case highlights the diagnostic complexity of gastrointestinal amyloidosis with multisystem involvement. The patient's presentation, along with elevated free light chains and monoclonal gammopathy, raised suspicion for AL amyloidosis, though chronic hepatitis B and possible lymphoproliferative disease kept AA amyloidosis in the differential. Consistent with the literature, vague gastrointestinal (GI) symptoms often delay diagnosis, underscoring the role of Congo red staining and mass spectrometry for confirmation and subtype identification. Recent trials support daratumumab for AL and patisiran/inotersen for ATTR amyloidosis. Early, accurate diagnosis is key to initiating appropriate therapy and improving outcomes, with multidisciplinary involvement crucial for optimal care.