MON-367 Unusual Presentation of Hypercalcemia Preceding the Diagnosis of Methotrexate-Induced Pneumocystis Jirovecii Pneumonia from Treatment of Necrotizing Myopathy

Background: Pneumocystis Jirovecii infection is a common opportunistic infection often seen severely immunocompromised individuals, such as those with HIV/AIDs. This is an unusual case where the patient displayed persistent hypercalcemia, with an eventual diagnosis of PCP likely due to immunosuppression from methotrexate (MTX) therapy. Case: A 79 year old male was brought to the hospital for acute change in mental status and hypercalcemia (13.4mg/dl). The patient was acutely encephalopathic, oriented to self only; his baseline was a high level executive at a company. An extensive neurologic workup including CT, MRI, EEG, spinal fluid examination was negative with a persistent hypercalcemia. Additional workup showed no increase in bone turnover, suppressed PTH, non-elevated pPTHrP. He was found to have diffuse mild PET avidity of bilateral lungs on PET scan, with bronchoscopy for evaluation of potential granulomatous disease. PCR of the BAL fluid obtained during bronchoscopy was positive, and the patient was ultimately treated with an extended course of Atovaquone for Pneumocystis Jirovecii pneumonia (PCP). The patient was felt to have an immunosuppressed state secondary to being treated for a necrotizing myopathy with methotrexate. The patient’s mentation slowly but substantially improved with a combination of a prednisone taper and Atovaquone, with discontinuation of the MTX. The patient’s hypercalcemia improved with treatment of PCP. Conclusion: Although a cause of hypercalcemia secondary to primary hyperparathyroidism causing necrotizing myopathy is known in the literature, it is unusual to see the opposite, where few case reports have documented hypercalcemia due to immunosuppression from low-dose methotrexate treatment for necrotizing myopathy resulting in pulmonary pneumocystis and hypercalcemia. Additionally, MTX induced immunodeficiency is often associated with severe immunosuppression or lymphoproliferative disorders - however the patient had an extensive work up with negative results for malignancy