Mucormycosis-induced hypercalcemia: a case report

Hypercalcemia is a vital laboratory marker because it can show underlying severe diseases like cancer and infections. Of all the causes of hypercalcemia, primary hyperparathyroidism, and malignancies are the most common, but granulomatous diseases, such as certain fungal infections, can also be the cause. Here we describe the case of a 29-year-old woman, an insulin-dependent diabetic, found unconscious and tachypneic at home. In the emergency room, the medical team diagnosed diabetic ketoacidosis (DKA) and acute kidney injury (AKI). During hospitalization, despite resolving acidemia, persistent hypercalcemia attracted attention. Laboratory tests showed decreased parathyroid hormone (PTH) levels, confirming non-PTH-dependent hypercalcemia. Computed tomography (CT) of the chest and abdomen demonstrated no alterations, but an upper digestive endoscopy revealed an ulcerated and infiltrative lesion in the stomach. A biopsy showed a granulomatous infiltrate due to mucormycosis infection. The patient received liposomal amphotericin B for 30 days and isavuconazonium for two months. Serum calcium levels improved during treatment. Inquiry of the etiology of hypercalcemia should begin with the PTH assay; high levels are consistent with hyperparathyroidism; low levels, with calcium or vitamin D intoxication, malignancies, prolonged immobilization, and granulomatous diseases. In the latter cases, the overproduction of 1-alpha-hydroxylase by the granulomatous tissue increases the conversion of 25(OH)vitamin D into 1-25(OH)vitamin D, which causes the intestinal absorption of calcium. We have described the first hypercalcemia related to mucormycosis infection in a young diabetic patient, although case presentations associate other fungal infections with elevated serum calcium.