Rickets involves defective bone mineralisation at the growth plates in children, resulting in skeletal deformity. It is associated with soft and weak bones.
Causes
Rickets is caused by a deficiency in vitamin D, calcium or phosphate. Vitamin D is either produced by the body in response to sunlight or obtained through foods such as eggs, oily fish or fortified cereals or nutritional supplements. Calcium is found in dairy products and some green vegetables.
There is a rare form of rickets, called hereditary hypophosphataemic rickets, caused by genetic defects that lead to low phosphate levels in the blood. The most common form is X-linked dominant, although there are other modes of inheritance.
Simplified Pathophysiology
Vitamin D is a prohormone the skin creates in response to sunlight. It is also obtained in limited amounts from food. It is vital in regulating bone mineralisation, hormone secretion and immune function. Low vitamin D is very common.
Vitamin D is created from cholesterol by the skin in response to UV radiation. Patients with darker skin require longer sun exposure to generate the same amount of vitamin D. It is also obtained from food as a fat-soluble vitamin. A regular diet does not contain enough vitamin D to compensate for reduced sun exposure.
Patients with malabsorption disorders (e.g., inflammatory bowel disease) are at higher risk of vitamin D deficiency. Patients with chronic kidney disease are also at higher risk, as the kidneys help convert vitamin D into its active form.
Vitamin D is essential in calcium and phosphate absorption in the intestines and reabsorption in the kidneys. It is also responsible for regulating bone turnover and promoting bone resorption to increase the serum calcium level.
Inadequate vitamin D can lead to low serum calcium and phosphate. Since calcium and phosphate are required for bone formation, low levels lead to defective bone mineralisation and osteomalacia.
Low calcium leads to increased parathyroid hormone (PTH) secretion by the parathyroid glands (secondary hyperparathyroidism). Parathyroid hormone promotes calcium resorption from the bones, further impairing bone mineralisation. Serum calcium may be normal despite relative deficiency.
Presentation
Patients with vitamin D deficiency and rickets may not have any symptoms. Potential symptoms include:
- Lethargy
- Bone pain
- Swollen wrists
- Bone deformity
- Poor growth
- Delayed walking
- Dental problems
- Muscle weakness
- Pathological or abnormal fractures
Bone deformities that can occur in rickets include:
- Bowing of the legs, where the legs curve outwards
- Knock knees, where the legs curve inwards
- Rachitic rosary, where the ends of the ribs expand at the costochondral junctions, causing lumps along the chest
- Craniotabes (a soft skull), delayed fontanelle closure and frontal bossing
- Delayed tooth eruption with under-development of the enamel
Investigations
Serum 25-hydroxyvitamin D is the laboratory investigation for vitamin D:
- Less than 25 nmol/L – vitamin D deficiency
- 25 to 50 nmol/L – inadequate vitamin D
Other blood results include:
- Serum calcium may be low
- Serum phosphate may be low
- Serum alkaline phosphatase may be raised
- Parathyroid hormone may be raised
If rickets is suspected clinically, an x-ray of the wrist or knee can confirm active rickets by showing growth-plate and metaphyseal changes.
Management
Prevention is the best management for rickets. All children aged 0-4 years are recommended to take a daily supplement containing vitamin D:
- 340–400 IU (equivalent to 8.5-10 mcg) for infants under 1 year
- 400 IU (equivalent to 10 mcg) for children aged 1-4 years
Formula milk is fortified with vitamin D, meaning that additional supplementation is not required in babies taking at least 500 mL daily of formula.
Children with vitamin D deficiency can be treated with vitamin D (colecalciferol). A loading regimen may be used to boost vitamin D levels when rapid correction is required, with higher doses for 8-12 weeks. The doses depend on the child’s age. For example, the loading regime for children aged 6 months to 11 years is 6000 IU daily. The loading regimen should be followed by maintenance supplementation.
Children with features of rickets should be referred to a specialist. Vitamin D and calcium are used to treat rickets.
Last updated July 2026
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