CYP27B1 and sarcoidosis: Conversion of inactive vitamin D to its active form requires the enzyme 1-alpha-hydroxylase (also known as cytochrome p450 27B1 or CYP27B1), which is present in renal tubular cells, but can also be found at multiple extrarenal sites, including in immune cells involved in granulomatous diseases, like the alveolar macrophages of patients with sarcoidosis [11,12].