Type I vitamin D dependent rickets. Rickets may occur when the supply of vitamin D is inadequate, its metabolism is abnormal, or the body is resistant to its actions. In vitamin D deficient rickets, the reduced vitamin D intake causes a decrease in the absorption of calcium from the GI tract. In hypophosphatemic vitamin D resistant rickets, there is a physiologic problem with the re-absorption of phosphate from the proximal tubule of the kidneys. Infants with vitamin D deficiency experience decreased growth, short stature, bowing of the legs, and poor weight gain.
Some infants have seizures or tetany due to low calcium levels.
In advanced cases, knock-knees, chest deformities, and short stature may be permanent. In hypophosphatemic vitamin D resistant rickets, the affected child has a very short stature and severe bowing of the legs. Children with this type of rickets will also experience abnormal dentin formation which results in delayed dental eruption and spontaneous dental abscesses. X-rays will demonstrate changes in the bones, which appear before any overt physical signs. In vitamin D deficient rickets, the alkaline phosphatase level in the serum is elevated.