A Dimorphic Diagnosis of a Pleomorphic Disease: An Unusual Cause of Hypercalcemia

Histoplasmosis is a rare cause of 1, 25-dihydroxy vitamin-D-mediated hypercalcemia. In this study, we report 2 cases of hypercalcemia secondary to histoplasmosis seen at Mayo Clinic, Rochester and a review of cases reported in the literature. We conducted a PubMed search using the keywords “hypercalcemia” and “histoplasmosis.” Fourteen cases of hypercalcemia secondary to histoplasmosis were reported between 1977 and 2020. We identified an additional 2 patients from our institution. We reviewed a total of 16 cases. The median age at presentation was 58.5 years (interquartile range, 41.5-68.75 years), and 13 of 16 patients (81.2%) were men. Serum parathyroid hormone level was available in 13 of 16 (81.25%) patients, of whom 11 patients (84.6%) had a low level, 1 patient (7.6%) had a normal level, and 1 patient (7.6%) had an elevated level. 1, 25-dihydroxy vitamin D level was reported in 9 of 16 (56.25%) patients. Of these, 5 patients (55.5%) had levels within normal limits, and 4 patients (44.4%) had levels above normal. Serum angiotensin-converting enzyme level was evaluated in 4 of 16 patients (25%), and it was elevated in all 4 (100%) cases. Four patients received corticosteroids before a diagnosis of histoplasmosis was made, which resulted in rapidly progressive disease and death in 2 patients. In patients with granulomatous disorder and hypercalcemia, it is crucial to rule out infectious etiologies before initiating steroids. Histoplasmosis can cause nonparathyroid hormone-mediated hypercalcemia and, if not suspected, may have catastrophic implications.