Rickets can be classified as Vitamin D deficiency (Nutritional rickets), Vitamin D dependent rickets (type 1 and 2)and Hypophosphatemic rickets. Nutritional rickets is characterised by raised alkaline phosphatase, low phosphorus and in late stages, low calcium. Response to vitamin D is seen in a couple of weeks. If there is no response then other causes of rickets should be considered.
Hypophospahetmic rickets is charaterised by severe hypophosphatemia and absence of secondary hypoparathyroidism with impaired renal reabsorption of phosphate.
Vitamin D dependent rickets- Type 1 is characterised by severe hypocalcemia, secondary hyperparathyroidism, decreased serum 1,25-dihydroxyvitamin D3, normal serum 25-hydroxyvitamin D3.
Vitamin D dependent rickets – type 2 is characterised by normal 25-hydroxyvitamin D3, increase in the circulating 1,25-dihydroxyvitamin D3 and alopecia is seen in half of the patients.