Systemic Sarcoidosis Presenting With Hypercalcemia, Acute Kidney Injury, and Diffuse Lymphadenopathy: Unlocking Pandora's Box.

Sarcoidosis is a rare granulomatous disease with complex pathogenesis, nonspecific manifestations, and systemic sequelae leading to difficulties in differential diagnosis and increased potential for misdiagnosis. Renal involvement consists of an uncommon and underreported condition, especially in the absence of other extra-renal manifestations. Herein, we describe the case of a 58-year-old Caucasian female who presented with acute kidney injury alongside persistent hypercalcemia, diffuse lymphadenopathy, and B symptoms, namely, unintentional weight loss, fever, and fatigue. The laboratory findings revealed elevated creatinine and calcium levels, suppressed intact parathyroid hormone (iPTH) and increased calcitriol and angiotensin-converting enzyme (ACE) levels, raising suspicion of sarcoidosis. Renal biopsy revealed the presence of non-necrotizing granulomas, a pattern compatible with the diagnosis of sarcoidosis granulomatous interstitial nephritis (sGIN). Combined therapy with corticosteroids and hydroxychloroquine was initiated, and the patient's follow-up showed significant improvement in kidney function without relapses, highlighting the importance of early disease recognition and intervention. This case study unveils the diagnostic odyssey of the clinician to establish the diagnosis of sarcoidosis and prompts them to include such a diagnosis in their differential diagnosis algorithm in patients presenting with acute kidney injury, diffuse lymphadenopathy, and non-PTH-mediated hypercalcemia.