99mTc-HSA scintigraphy identifies protein-losing enteropathy in atypical GI-GVHD with modest diarrhea after allo-HSCT

Protein-losing enteropathy (PLE) is an uncommon but clinically important manifestation of gastrointestinal graft-versus-host disease (GI-GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We report two cases of progressive hypoalbuminemia despite only modest diarrhea after allo-HSCT. The first patient was a 33-year-old man with refractory acute myeloid leukemia who underwent haploidentical sibling donor allo-HSCT and subsequently developed modest diarrhea and progressive hypoalbuminemia despite corticosteroid therapy. Although endoscopy revealed abnormal whitish duodenal villi, biopsy findings were inconclusive for GI-GVHD, possibly because of prior corticosteroid treatment. The second patient was a 65-year-old woman with refractory diffuse large B-cell lymphoma who underwent HLA-matched unrelated donor allo-HSCT and developed modest diarrhea. Lower gastrointestinal endoscopy and histological findings were consistent with GI-GVHD, but hypoalbuminemia progressed despite systemic corticosteroid therapy. In both cases, 99 m-labeled human serum albumin (99mTc-HSA) scintigraphy demonstrated abnormal intraluminal radiotracer accumulation in the small intestine, providing objective evidence of enteric protein loss and supporting the diagnosis and escalation of GVHD-directed therapy. Hypoalbuminemia improved after treatment with hMSC therapy, with or without ruxolitinib. These cases suggest that 99mTcHSA scintigraphy may be useful for evaluating suspected GI-GVHD-associated PLE when stool volume underestimates disease severity.