Hypercalcaemia preceding diagnosis of Pneumocystis jirovecii pneumonia in renal transplant recipients

Background: The overall incidence of Pneumocystis jirovecii pneumonia (PJP) in solid organ transplant recipients is 5–15%.A timely diagnosis of PJP is difficult and relies on imaging and detection of the organism.Methods: We present a case series of four patients displaying hypercalcaemia with an eventual diagnosis of PJP and documentthe management of the outbreak with a multidisciplinary team approach. We discuss the underlying pathophysiologyand previous reports of hypercalcaemia preceding a diagnosis of PJP. We also reviewed the evidence concerning PJP diagnosisand treatment.Results: Within our renal transplant cohort, four patients presented within 7months with hypercalcaemia followed by aneventual diagnosis of PJP. We measured their corrected calcium, parathyroid hormone (PTH), 1,25-dihydroxycholecalciferol[1,25-(OH)2D3] and 25-hydroxycholecalciferol [25(OH)D] levels at admission and following treatment of PJP. All four patientsdiagnosed with PJP were 4–20 years post-transplantation. Three of the four patients demonstrated PTH-independent hypercalcaemia(corrected calcium >3.0mmol/L). The presence of high 1,25(OH)2D3 and low 25(OH)D levels suggest negation ofthe negative feedback mechanism possibly due to an extrarenal source; in this case, the alveolar macrophages. All fourpatients had resolution of their hypercalcaemia after treatment of PJP.Conclusions: Given the outbreak of PJP in our renal transplant cohort, and based on previous experience from other unitsnationally, we implemented cohort-wide prophylaxis with trimethoprim–sulphamethoxazole for 12months in consultationwith our local infectious diseases unit. Within this period there have been no further local cases of PJP