Types of rickets are important to know and understand.
To define, rickets is bony manifestation of altered vitamin D, calcium and phosphorous metabolism in a child leading to inadequate mineralization of bone.
Four different types of rickets on the basis of etiology are
- Nutritional
- Hereditary vitamin D deficiency
- Familial Hypophosphatemic rickets, and
- Hypophosphatasia
Nutritional rickets
This may occur either due to deficiency of vitamin D, calcium or phosphorus in the diet. Hence, three different types.
There is increase in Alkaline phosphatase (ALP) and parathyroid hormone (PTH). However, calcium, phosphorus and vitamin D are on lower range.
Hereditary vitamin D deficiency rickets
The symptoms may be similar to earlier form but quite severe. There may be baldness also. It has further two types:
- Type I: defect in renal 25(OH)-vitamin D 1α-hydroxylase. Thus, this form inhibits conversion of inactive Vitamin D into its active form. It has autosomal inheritance. Further, it affects chromosome 12q14.
- Type II: There is receptor defect for 1,25(OH)2-vitamin D3
Another type of rickets is familial hypophosphatemic rickets
In this form, there is there is X-linked dominant inheritance. Miller’s Review of Orthopaedics quotes this as the most common form of rickets.
Biochemically, there is increase in ALP and normal serum calcium. However, there is decrease in vitamin D and phosphorus in this type.
Hypophosphatasia
This autosomal recessive disorder, presents with decline in the levels of ALP. To diagnose, there must be an increase in urinary phosphoethanolamine levels.
Features are similar to that of nutritional rickets and phosphate therapy is the treatment.