Background: We describe a case of a fever of unknown etiology that was caused by a caseating tubercle\r\ngranuloma which produced erythropoietin. To our knowledge, this is the first report of an erythropoietinproducing\r\ngranuloma.\r\nCase presentation: A 48-year-old Japanese man with a 5-year history of maintenance hemodialysis for diabetic\r\nnephropathy presented with an intermittent fever over a few months. During febrile periods he developed erythema\r\nnodosum on his legs. Computed tomography showed axillary lymph node enlargement and this was further\r\ncorroborated by a gallium scan that revealed high gallium uptake in these nodes. A Mantoux test was positive and an\r\ninterferongamma release assay for tuberculosis diagnosis was also positive. Lymph node tuberculosis was suspected and\r\nthe patient underwent lymphadenectomy. Histological analysis of the lymph nodes revealed a caseating granuloma that\r\nshowed positive results on an acid-fast bacteria stain and a Mycobacterium tuberculosis polymerase chain reaction test.\r\nAfter lymphadenectomy, however, the patient�s hemoglobin levels rapidly decreased from 144 to 105 g/L, and this was\r\nfurther compounded by a decrease in serum erythropoietin from 223 mIU/mL to 10.7 mIU/mL by postoperative day 21.\r\nWe suspected the tubercle to be a source of the erythropoietin and this was further confirmed by in situ hybridization.\r\nConclusions: We report for the first time ectopic erythropoietin production by a tuberculous lymph node. Our\r\nobservations are substantiated by a postoperative decline in his erythropoietin level and a clinical requirement for\r\nerythropoietin treatment.
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