This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
Vitamin D resistant rickets occurs due to all Except 
Select and explain. 
A. alpha 1 hydroxylase deficiency, B. Renal tubular acidosis, C. Fanconi syndrome, D. Drugs
A: alpha 1 hydroxylase deficiency
Answer: A: alpha 1 hydroxylase deficiency 
Explanation: The disorder is due to missing or inactive PHEX gene. PHEX inactivates phosphatonins that mediate phosphate wasting. Thus, patients with Vitamin D resistant rickets cannot retain phosphate, leading to renal phosphate wasting. ref - Harrisons internal medicine 20e p2920