Objective:
Vitamin D is essential for bone development and health, and deficiency resulting in rickets and skeletal deformities is seen mainly during rapid growth. Hereditary vitamin D dependent rickets type I and type II rickets is a very rare form of rickets, characterized by 1-alpha-hydroxylase deficiency or end-organ resistance to vitamin D. We aimed to investigate, clinical and laboratory characteristics of eight cases with Vitamin D-dependent rickets (VDRR).

Method:
The mean age of patients during diagnosis was 2.6 years. Excluding one patient, others were males (87.5%).

Results:
Mean laboratory values during referral was calcium 7.5±1,5 mg/dl, phosphorus 4±1.2 mg/dl, alkaline phosphatase (ALP) 1679±641 U/L and parathyroid hormone (PTH) 524±498 pg/ml. Patients received 1.2 µg/kg/day calcitriol. During follow-ups serum ALP and PTH values of patients turned to normal levels.

Conclusion:
In rickets, cases with persistent increased serum ALP and PTH levels it will be appropriate to investigate serum 25 (OH) D levels in cases diagnosed with vitamin D-dependent rickets even though hypocalcaemia is absent. Administration of adequate doses of calcitriol in some cases is able to clinical and laboratory values return to normal.