Rickets is a clinical syndrome of deformities of growing bones and delayed physical milestones usually caused by a lack of vitamin D. Vitamin D is present in a mixed diet and can be made in the skin if the child is exposed to sunlight. In South Africa nutritional rickets is usually seen in preterm infants who are exclusively breastfed and not exposed to sunlight. Breast milk contains little vitamin D. Infant formulas are supplemented with vitamin D. Once infants start walking, they usually have adequate sun exposure to make their own vitamin D.
Rickets in infants presents with soft, deformed bones, resulting in:
- A ‘rickety rosary’ with swelling of the ribs where bone meets cartilage
- A chest deformity with a horizontal groove overlying the diaphragm attachment to the ribs (Harrison’s sulcus)
- Craniotabes with a softened ‘ping-pong’ skull above the ears
- Thickened wrists and ankles
- Decreased muscle tone, giving a distended abdomen
- Delayed physical milestones
- An increased risk of pneumonia
Treatment consists of 1000 units of oral vitamin D daily for a month by which time there should be radiological confirmation of healing. Increase exposure to sunlight for 30 minutes a week. For prevention vitamin D 400 units daily (in 0.6 ml of multivitamin drops or 5 ml vitamin syrup) should be given to preterm infants for 6 months as they are at high risk of developing rickets.
Rickets due to calcium deficiency can occur in older children on a diet which has adequate vitamin D but is low in calcium (e.g. maize without milk). There are also rare renal and metabolic causes of rickets in children who do not respond to the standard treatment. Vitamin D deficiency in adolescents (osteomalacia) presents with bone pain, muscle weakness and hypotonia. Hypovitaminosis D can be confirmed by finding a low concentration of serum 25 hydroxycholecalciferol.