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 document the management of the outbreak with a multidisciplinary team approach. We discuss the underlying pathophysiology and previous reports of hypercalcaemia preceding a diagnosis of PJP. We also reviewed the evidence concerning PJP diagnosis and treatment.

Results: Within our renal transplant cohort, four patients presented within 7months with hypercalcaemia followed by an eventual 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 patients diagnosed 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 of the negative feedback mechanism possibly due to an extrarenal source; in this case, the alveolar macrophages. All four patients 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 units nationally, we implemented cohort-wide prophylaxis with trimethoprim–sulphamethoxazole for 12months in consultation with our local infectious diseases unit. Within this period there have been no further local cases of PJP.