Lung-uptake and -washout of MIBG in sarcoidosis

BACKGROUND: The aim of this study was to evaluate the uptake and -washout of I-123 meta-iodobenzylguanidine (MIBG), reflecting norepinephrine metabolism, in the lungs in patients with sarcoidosis. METHODS: Lung I-123 MIBG kinetics was assessed in 43 patients with sarcoidosis. The range of disease duration was 1-16 years (median: 3 years). Thirteen patients had radiographic stage 0-I, 30 patients had radiographic stage II-IV. Serological clinical parameters and small fibre neuropathy, as assessed by temperature threshold testing (TTT) were measured in 39/43 patients. 31/39 patients had an abnormal TTT. Eleven healthy controls participated in this study. Both dual head planar and dual headed SPECT images of the thoracic regions were made. The uptake of I-123 MIBG and the washout percentage were calculated in sarcoidosis patients and compared with the healthy persons. RESULTS: Lung I-123 MIBG uptake in patients with sarcoidosis did not differ from controls. The lung washout of I-123 MIBG was significantly (p<or=0.01) decreased in sarcoidosis. Remarkably this was most clearly seen in patients with an abnormal TTT and in patients with more advanced radiographic pulmonary involvement (radiographic stages II-IV) but not in patients with decreased lung function (FVC<80% or DLCO<80%). CONCLUSION: The inflammatory process of the lungs in sarcoidosis seems not to affect pulmonary vasculature. In sarcoidosis decreased lung washout of I-123 MIBG might, at least partly, be explained by sympathetic autonomic nerve dysfunction. Future studies are needed to explore the clinical relevance of this observation.