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Fluorine-18-fluorodeoxyglucose positron emission tomography as a novel noninvasive diagnostic tool for gastrointestinal graft-versus-host disease.

Gastrointestinal graft-versus-host disease (GVHD) represents a serious complication after allogeneic hematopoietic stem cell transplantation. Histological diagnosis from endoscopically obtained specimens remains the gold standard despite technical and methodical limitations (1). Here, we report on a 52-year-old woman receiving an unmodified, T-cell replete bone marrow transplantation from a haploidentical family donor for secondary acute myeloid leukemia. The preparative regimen consisted of fludarabine (30 mg/m/d), high-dose cytosine arabinoside (2000 mg/m/d) for 5 days and low-dose total-body irradiation (2 Gy) with posttransplant immunosuppression with cyclophosphamide (50 mg/kg) on day 3 followed by tacrolimus and mycophenolate mofetil as described previously (2). Successful neutrophil engraftment defined as the first of 2 consecutive days with an absolute neutrophil count 0.5 g/L was documented on day 20 and short-tandem repeat analysis of peripheral blood revealed full donor chimerism (97%) on day 30 (3). The early posttransplantation period was complicated by watery diarrhea ( 1500 mL/d) and crampy abdominal pain starting around day 35, consistent with the clinical diagnosis of acute gastrointestinal GVHD III°–IV°. Serial tests of stool for bacterial, common viral (including cytomegalovirus) or fungal pathogens were repeatedly negative. An immediately performed endoscopy was nondiagnostic because of the insufficient quality of the obtained biopsies. Of note, the patient was still platelettransfusion dependent (PH10 g/L) at this time. For further diagnosis, fluorine-18fluorodeoxyglucose positron emission tomography (FDG-PET) was conducted, showing significant FDG uptake in the ascending colon, the right side of the transverse colon, the terminal ileum, as well as in the inferior part of the left lung (Fig. 1). The latter lesions were probably consistent with asymptomatic GVHD of the lung and impressed as nonspecific patchy infiltrates on computed tomography scan of the chest (4). Because the patient’s diarrhea was refractory to systemic (2 mg/kg/d) and topical steroids, antithymocyte globulin (ATG Fresenius®, 1 mg/kg/d) was added for 7 consecutive days. After clinical improvement FDG-PET was repeated, showing a complete resolution of increased FDG uptake in all former lesions. The patient was discharged on day 50 without evidence of ongoing GVHD under slowly tapering steroids. Gastrointestinal endoscopy and biopsy are mandatory for proper diagnosis of upperand lower-tract disease (5, 6). However, accurate diagnosis is limited by methodical and technical problems. Biopsies of the gastrointestinal tract should at least extend to muscularis mucosa to ensure adequate histological architecture for review, which frequently is hampered by presence of thrombocytopenia and thus an increased risk for bleeding postbiopsy (7). Another reason for inadequate diagnosis might be the fact that GVHD is limited to different parts of the intestine that are not identified by endoscopy. Noninvasive tools for the diagnosis of intesti-