SUN-788 Hypercalcemia with Elevated 1,25-Dihydroxyvitamin D in a Patient with Disseminated Coccidiomycosis

Abstract Disclosure: G. Reddy: None. G. Gill: None. H. Tabassum: None. K.L. Vinales: None. Hypercalcemia is an uncommon but recognized complication of granulomatous diseases such as sarcoidosis and tuberculosis, mediated by elevated 1,25-OH vitamin D. Disseminated coccidiomycosis is a rarely reported granulomatous cause of hypercalcemia, with only a few case reports and case series, all of which describe patients with normal or low 1,25-OH vitamin D level. The underlying pathophysiology is not clearly understood but has been suggested to be PTHrP-mediated. We present a unique case of disseminated coccidiomycosis with low PTHrP and elevated 1,25-OH vitamin D. A 69-year-old male with hypertension, hyperlipidemia, stage III chronic kidney disease, and autoimmune hepatitis status post liver transplant on immunosuppression was admitted for sepsis and respiratory failure secondary to disseminated coccidiomycosis. On initial evaluation, he was alert without acute distress. Chest imaging depicted miliary nodules and mediastinal adenopathy consistent with coccidiomycosis. Admission labs showed an adjusted serum calcium of 9.6 mg/dL for albumin 3.1 g/dL, HCO3 19 mmol/L, and acute kidney injury (AKI) with creatinine 2.25 mg/dL and eGFR 31 mL/min (baseline 1.5 mg/dL). Coccidiomycosis EIA and ID IgM and IgG were positive. MRSA screen, influenza, Pneumocystis jirovecii PCR, Aspergillus PCR, urine Legionella/Streptococcus antigen, QuantiFERON-TB Gold, cryptococcal serum antigen, acid-fast bacilli, and blood cultures were negative. An IR-guided liver biopsy revealed granulomatous hepatitis indicative of coccidioidomycosis. Skeletal survey was unremarkable for bony lesions, and a bone marrow biopsy with flow cytometry showed no significant immunophenotypic abnormality or monoclonal plasma cells. By hospital day 13, serum calcium rose to 12.3 mg/dL (ionized calcium 6.69 mg/dL). Treatment with IV fluids, IV furosemide, intermittent hemodialysis, and one dose of denosumab 120 mg (day 16) was initiated, but serum calcium failed to respond and peaked at 13.4 mg/dL (ionized calcium 7.46 mg/dL) on hospital day 17. Additional labs showed low PTH (8 pg/mL), low PTHrP (6 pg/mL), elevated phosphorus (5.9 mg/dL), low-normal 25-OH vitamin D (30 ng/mL), and elevated 1,25-OH vitamin D (82 pg/mL). Magnesium and bone-specific ALP were normal. Given his elevated 1,25-OH vitamin D, a 20 mg/day course of oral prednisone was initiated, followed by a prompt serum calcium drop to 12.5 mg/dL (ionized calcium 7.09 mg/dL) on day 2, with complete normalization by day 5 of prednisone. The patient completed a total 7-day course of prednisone therapy followed by a 5-day taper, and serum adjusted calcium remained normal at his 1-month follow-up without necessitation for further treatment. This case suggests that hypercalcemia in disseminated coccidiomycosis may have a more complex pathophysiology than previously thought and further investigation is needed to fully understand this condition. Presentation: Sunday, July 13, 2025