How to Recognize SABM

Background: Serous atrophy of bone marrow (SABM), also known as gelatinous transformation of bone marrow, is a disorder associated with severe and prolonged malnutrition states, such as cachexia or anorexia nervosa. Hematopoietic cells and adipocytes normally found in marrow are replaced by hyaluronic acid-rich gelatinous substance. Although considered rare, incidence has increased from 0.2% to 4.8% in recent studies. Its MRI apprearance is unusual and often misinterpreted as technical artifact from failed fat suppression or misidentified as an infiltrative malignant process. Objective: To review the imaging findings of SABM to improve diagnostic accuracy and reduce unnecessary, potentially invasive patient workup. Discussion: The characteristic finding on MRI for SABM is known as a "flip-flop" sign, where the normally diffuse T1-weighted hyperintense signal of bone marrow is reversed and the marrow appears diffusely hypointense relative to skeletal muscle. The marrow is also hyperin more...