Gastrointestinal Tract Amyloidosis Presenting With Pneumatosis Intestinalis

Pneumatosis intestinalis is a radiographic finding of gas pockets within the bowel wall. It can be associated with a range of diagnoses, but the most life-threatening causes are mesenteric ischemia, bowel necrosis, and bowel obstruction. Here we present the case of a patient with multiple myeloma who had pneumatosis intestinalis due to gastrointestinal amyloidosis, which is a rare manifestation of systemic amyloid disease. The patient had both transthyretin (ATTR) amyloidosis and acquired apolipoprotein serum amyloid A (AA) amyloidosis that are not usually seen in conjunction with multiple myeloma, which is most commonly associated with light-chain (AL) amyloidosis. This case highlights the importance of considering Congo red staining of bowel biopsies for amyloid deposition in patients undergoing endoscopy for unexplained gastrointestinal tract symptoms and even pneumatosis intestinalis, so as to avoid a delay in diagnosis that is typically seen with amyloidosis. Since each subtype of amyloidosis requires different therapy, amyloid subtyping is crucial, even with co-existing multiple myeloma.