Intractable hypercalcemia in a patient with multiple myeloma: An infectious etiology.

Hypercalcemia is a common laboratory finding in patients with malignancy, as well as with granulomatous disease. We report the case of a 75-year-old man with multiple myeloma (MM) who presented with generalized weakness, fever, and intractable hypercalcemia. The hypercalcemia proved difficult to treat despite well-controlled MM, as well as adequate use of bisphosphonates and calcitonin. Biopsy of sub-centimeter mesenteric adenopathy was significant for Histoplasma capsulatum and negative for malignancy, suggesting disseminated gastrointestinal histoplasmosis as the sole etiology for uncontrolled hypercalcemia. He was successfully treated with voriconazole. Disseminated histoplasmosis can be fatal if left untreated and warrants vigilance of non-malignant etiologies of hypercalcemia. While hypercalcemia is a common clinical manifestation of MM, our patient is an exemplar of maintaining a broader differential diagnosis in immunocompromised hosts.