Case history/examination:
A 67-year-old woman presented with increased serum creatinine level and elevated erythrocyte sedimentation rate (ESR), which was detected during routine follow-up. She did not complain of fever, weight loss, or any urinary symptoms. Except for an impalpable spleen, physical examination was otherwise normal. Her past medical history was positive for mild hypertension and antiphospholipid antibody syndrome (APAS) that had resulted in habitual abortion and thrombophlebitis of both lower extremities during pregnancy. The patient also reported a history of splenectomy following a motor vehicle accident. Approximately four years ago, during routine examinations, an abnormally high ESR (>75 mm/hour) was accidentally noticed, for which, considering her history of APAS, 10 mg oral prednisolone and 50 mg oral azathioprine was administered on daily basis. Although the patient had remained symptomless, a gradual rise in ESR was observed after one year from initiation of medical treatment. Further evaluation with computed tomography (CT) imaging had revealed a left renal mass that measured approximately 2-3 cm in size; however, the patient had refused to undergo further assessment and continued receiving medical treatment.