All are the causes of nephrocalcinosis in granulomatous disease except -: (A) Increased absorption of ca from intestine, (B) Increased conversion to 1,25 (OH )2 D, (C) Increased bone resorption, (D) Mutation in calcium sensing receptor
Answer is D. In granulomatous diseases ,granulomas have 1alpha hydroxylase activity . So there is increased conversion of 25(OH) D to 1,25(OH) 2 D. Increased active vitamin d INCREASES-reabsorption of calcium in PCT, bone resorption ,absorption of ca in intestine-resulting in hypercalcemia. Hypercalcemia results in-nephrocalcinosis, nephrolithiasis ,nephrogenic diabetes insipidus . Ref:Harrison 20 th edition pg no 2603