Hypercalcemia occurs in 10 to 30% of renal transplant recipients and i
s most often due to persistent hyperparathyroidism. Herein we describe
a patient with a history of hyperparathyroidism who sought medical as
sessment because of recurrence of hypercalcemia 7 Sears after a succes
sful renal transplantation, The hypercalcemia was associated with a no
rmal serum phosphate level, a low to normal parathyroid hormone level,
virtually undetectable levels of parathyroid hormone-related protein,
and increased 1,25-dihydroxyvitamin D levels, Further assessment led
to the diagnosis of an underlying lymphoma, To our knowledge, this is
the first report of 1,25-dihydroxyvitamin D-mediated hypercalcemia in
a renal transplant recipient with lymphoma, The possibility of an unde
rlying lymphoproliferative disorder should be considered in the differ
ential diagnosis of hypercalcemia in a renal transplant recipient.