CYP27B1 and Hypercalcemia: However, she unexpectedly developed severe hypercalcemia with high 1,25-dihydroxyvitamin D, suggesting a nonregulated activity of 25-hydroxyvitamin D3 1-alpha-hydroxylase, which catabolizes the transformation of 25-OH vitamin D into the biologically active 1,25-dihydroxyvitamin D. After we excluded diseases commonly responsible for such ectopic activity, we suspected that the malakoplakia cells expressed the enzyme as in other granulomatous diseases such as sarcoidosis or mycobacterial infections,[19] which was confirmed by immunostaining.