Multisystem Sarcoidosis Presenting With Hypercalcemia, Lytic Bone Lesion, and Mesenteric Panniculitis in Chronic Kidney Disease

ABSTRACT Sarcoidosis is a multisystem granulomatous disease that can closely mimic both malignant and endocrine disorders. We present the case of a 77‐year‐old man with CKD stage 3b who was hospitalized for severe hypercalcemia, unintentional weight loss, and recent changes in bowel habits. Imaging revealed bulky mediastinal and abdominal lymphadenopathy, mesenteric panniculitis, and a lytic lesion at lumbar vertebrae 1 (L1), raising a strong suspicion for lymphoma or multiple myeloma. Laboratory evaluation showed suppressed parathyroid hormone and high‐normal 1,25‐dihydroxy‐vitamin D (calcitriol), suggestive of a granulomatous process. Mediastinal lymph node excision confirmed the presence of non‐caseating granulomas, establishing the diagnosis of sarcoidosis. The diagnostic evaluation was complicated by CKD, which interfered with the interpretation of serum free‐light chain results, and by newly diagnosed painless thyroiditis presenting with transient hyperthyroidism that initially confounded the etiology of hypercalcemia. The patient was not receiving calcium or vitamin D supplementation. Hypercalcemia responded to intravenous fluids, diuretics, pamidronate, and corticosteroids. This case underscores the importance of maintaining a high index of suspicion for sarcoidosis in patients with unexplained hypercalcemia and multisystem involvement and illustrates the diagnostic complexity introduced by coexisting CKD and overlapping endocrine abnormalities at the time of presentation.