Atypical presentation of PJP: hypercalcemia and kidney injury in an allogeneic stem cell transplant recipient.

Background: Pneumocystis jirovecii pneumonia (PJP) is an opportunistic infection that primarily affects immunocompromised individuals. Typical symptoms of PJP include the subacute onset of dyspnea, nonproductive cough, and low-grade fever. In hematology patients, particularly those who are allogeneic stem cell transplant recipients, the disease often presents with a more aggressive clinical course. While hypercalcemia has been documented as a manifestation of PJP in some solid organ transplant recipients, it has not been reported in hematology or stem cell transplant patients.

Case Presentation: Here, we present a case of PJP in a 56-year-old male allogeneic stem cell transplant recipient, who developed hypercalcemia and renal failure during the late post-transplant period. The patient had a history of allogeneic stem cell transplantation due to acute myeloid leukemia. He presented with symptoms of fatigue and weakness. Laboratory tests revealed hypercalcemia (13.8 mg/dL) and elevated serum creatinine levels (2.3 mg/dL). The patient was hospitalized, and despite initial treatment with hydration and furosemide, the hypercalcemia persisted, leading to the administration of denosumab. During follow-up, hypoxia was detected, and a chest CT scan revealed mosaic attenuation and ground-glass opacities. Bronchoscopy was performed, and PCR testing confirmed the presence of Pneumocystis jirovecii. Other causes of hypercalcemia were ruled out, with PTH measured at 13.8 pg/mL (normal range 15-65 pg/mL), albumin at 3.71 g/dL, 1.25-dihydroxy vitamin D3 at 96 ng/dL (normal range 26-95 ng/dL), and 25-hydroxy vitamin D at 32.5 ng/mL (normal range 20-40 ng/mL). A PET-CT scan demonstrated no pathological FDG uptake, with the exception of findings suggestive of a pulmonary infection. Following treatment with trimethoprim-sulfamethoxazole and denosumab, the patient's hypercalcemia and infection resolved.

Conclusions:  Although rare, PJP can present with hypercalcemia and kidney injury in allogeneic stem cell transplant recipients. Early diagnosis and treatment can improve both PJP and hypercalcemia.