This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
The cause of nephrocalcinosis in systemic granulomatous disease is: 
Select and explain. 
A. Overproduction of 1,25 dihydroxy vitamin D, B. Dystrophic calcification, C. Mutation in calcium sensing receptors, D. Increased reabsorption of calcium
A: Overproduction of 1,25 dihydroxy vitamin D
Answer: A: Overproduction of 1,25 dihydroxy vitamin D 
Explanation: Nephrocalcinosis is deﬁned as calciﬁcation of the renal interstitium and tubules. It is associated with hypercalcemia, which occurs due to overproduction of vitamin D.