Severe Hypercalcemia and Acute Kidney Injury in a Patient with Probable IgG4-Related Disease and Cholestatic Liver Injury: A Case Report.

We report a 54-year-old man with a history of urticaria, hyperlipidemia, and hypertension who was receiving regular bisoprolol, rosuvastatin, and verapamil. He initially developed severe hypercalcemia (18.56 mg/dL) and acute kidney injury (serum creatinine, 5.14 mg/dL) while in China. Following intravenous hydration and calcitonin, serum calcium normalized and renal function substantially improved. During hospitalization, he subsequently developed marked eosinophilia, severe thrombocytopenia, cholestatic liver injury, lymphadenopathy, and markedly elevated serum IgG4 (851 mg/dL). Extensive evaluation did not identify evidence of malignancy or infection. The overall findings raised clinical suspicion of IgG4-related disease (IgG4-RD) with possible hepatobiliary involvement and suspected immune-mediated thrombocytopenia. Ursodeoxycholic acid and fenofibrate were initiated when primary biliary cholangitis remained under consideration, followed by systemic corticosteroid therapy with dexamethasone. The patient's liver abnormalities, thrombocytopenia, eosinophilia, and systemic manifestations subsequently improved. However, definitive tissue confirmation of IgG4-RD was not obtained, and characteristic cholangiographic evidence of IgG4-related sclerosing cholangitis was unavailable because MRCP or ERCP was not performed. During six months of outpatient follow-up, renal function remained stable and no clinical or biochemical relapse was observed. This case highlights severe hypercalcemia and acute kidney injury as unusual presenting features in a patient with clinical suspicion of IgG4-RD and emphasizes the importance of cautious diagnostic interpretation when histopathological and cholangiographic confirmation is unavailable.