<prompt> Vitamin D resistant rickets occurs due to all Exceptalpha 1 hydroxylase deficiencyRenal tubular acidosisFanconi syndromeDrugs  <response>: 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 