title: False-positive accumulation of metaiodobenzylguanidine in a case with acute intermittent porphyria.
abstract: We report a 36-year-old woman presenting with hypertensive encephalopathy followed by bulbar palsy and quadriplegia. After an extensive screening for secondary causes of hypertension, the patient was suspected of having pheochromocytoma due to increased levels of catecholamines in the plasma and the urine, and positive (131)I-metaiodobenzylguanidine (MIBG) accumulation in the gallbladder. However, MIBG accumulation was not reproducible without any tumors accompanying this accumulation in the gallbladder. A diagnosis of acute intermittent porphyria was finally confirmed based on the characteristic pictures, increased urinary excretion of porphobilinogen, and identification of a heterozygous missense mutation of R173W in the hydroxymethylbilane synthase gene. This case highlights a pitfall in utilizing MIBG to detect a source of excessive catecholamine and also suggests the importance of having a complete clinical history and extensive work-up of any possible differential diagnosis. We also review the potential mechanism by which false-positive MIBG accumulation occurs.
authors.affiliation: The First Department of Medicine, Nagasaki University Graduate School of Biomedical Sciences, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Masuda
authors.forename: Rie
authors.initials: R
authors.lastname: Ota
authors.forename: Takao
authors.initials: T
authors.lastname: Ando
authors.forename: Naoto
authors.initials: N
authors.lastname: Maeda
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Horie
authors.forename: Toshiro
authors.initials: T
authors.lastname: Yoshimura
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Motomura
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kawakami
mesh_terms: D019797:3-Iodobenzylguanidine; D000310:Adrenal Gland Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging; D000328:Adult; D002395:Catecholamines / Q000378:metabolism; D003937:Diagnosis, Differential; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D011163:Hydroxymethylbilane Synthase / Q000235:genetics; D020343:Hypertensive Encephalopathy / Q000209:etiology; D007457:Iodine Radioisotopes; D020125:Mutation, Missense; D010375:Pedigree; D010673:Pheochromocytoma / Q000175:diagnosis / Q000000981:diagnostic imaging; D011162:Porphobilinogen / Q000652:urine; D017118:Porphyria, Acute Intermittent / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000235:genetics; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals
chemical_list: D002395:Catecholamines; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine; D011162:Porphobilinogen; D011163:Hydroxymethylbilane Synthase