Vitamin D Metabolite–Mediated Hypercalcemia With Suppressed Parathormone Concentration in Pneumocystis jiroveci Pneumonia After Kidney Transplantation

Abstract Pneumocystis jiroveci pneumonia (PJP) is a severe complication in immunocompromised hosts including transplant recipients. Hypercalcemia (HCa) is not a classic symptom of the disease. However, HCa (mean [SD; range], 2.90 [0.20; 2.71–3.17] mmol/L) was detected in 5 patients with PJP at diagnosis. The HCa was associated with decreased concentrations of circulating parathormone (PTH), from 294 (292) ng/L 3 to 6 months previously to 20 (23.5; 7–53) ng/L. Concentrations of 1,25-(OH)2 vitamin D, measured in 3 patients, were in the high normal range (54.66 [7.23; 225–66] μg/L), whereas 25-(OH) vitamin D concentrations were low (13.9 [2.17; 20–60] μg/L). After treatment with trimethoprim-sulfamethoxazole for 21 days, 4 patients recovered and 1 died. Calcium and PTH concentrations rapidly returned to normal (2.36 [0.05] mmol/L and 89 [29.7] ng/L, respectively) at 2 months after the acute phase of the disease. Although fewer than 10 cases of PJP-associated HCa have been reported to date, it is possible that this association is more frequent than previously thought because our cases were detected during 2 years. As in other granulomatous disease–induced HCa, including fungal infections, it is likely that endogenous extrarenal production of 1-α-hydroxylase by activated macrophages and by interferon-γ involved in granuloma formation results in increased conversion from 25-(OH) vitamin D to 1,25-(OH)2 vitamin D and, consequently, in transient HCa and suppression of PTH secretion. Fortuitous detection of HCa in transplant recipients with pulmonary symptoms must raise suspicion of PJP or fungal infection.