Rickets

Rickets is a childhood metabolic bone disease characterized by defective mineralization of the growing bone and growth plate before closure of the epiphyses. It is most commonly caused by vitamin D deficiency, although calcium deficiency, phosphate deficiency, chronic kidney disease, liver disease, and inherited disorders of vitamin D or phosphate metabolism may also cause rickets. Vitamin D facilitates intestinal absorption of calcium and phosphate, both of which are essential for normal bone mineralization. Inadequate mineralization results in soft, weak bones, skeletal deformities, impaired growth, and an increased risk of fractures.

Pathophysiology

Vitamin D deficiency reduces intestinal absorption of calcium and phosphate, leading to hypocalcaemia or relative calcium deficiency. This stimulates secretion of parathyroid hormone (secondary hyperparathyroidism), which increases bone resorption and renal phosphate excretion to maintain serum calcium levels. Persistent hypophosphataemia impairs mineralization of newly formed osteoid and the growth plate cartilage. Consequently, the growth plates become widened and disorganized, causing characteristic skeletal deformities, delayed growth, and bone pain. In severe or prolonged disease, muscle weakness, delayed motor development, pathological fractures, and permanent skeletal deformities may occur.

Risk factors

• Exclusive breastfeeding without vitamin D supplementation

• Inadequate dietary vitamin D or calcium intake

• Limited sunlight exposure

• Dark skin pigmentation

• Prematurity

• Malabsorption syndromes

• Chronic liver disease

• Chronic kidney disease

• Anticonvulsant therapy

• Hereditary disorders affecting vitamin D or phosphate metabolism

Clinical presentation

Clinical manifestations vary according to the severity and duration of disease.

Infants

• Delayed motor milestones

• Irritability

• Poor feeding

• Hypotonia

• Craniotabes

• Delayed closure of fontanelles

• Delayed tooth eruption

• Hypocalcaemic seizures (severe deficiency)

Children

• Delayed linear growth

• Bone pain and tenderness

• Muscle weakness

• Difficulty walking

• Waddling gait

• Bow legs (genu varum)

• Knock knees (genu valgum)

• Wrist and ankle widening

• Frontal bossing

• Rachitic rosary

• Harrison sulcus

• Spinal deformities

• Pelvic deformity

• Pathological fractures in severe disease

Diagnostic criteria

Rickets is diagnosed using a combination of clinical features, biochemical abnormalities, and radiological findings.

Clinical criteria

• Age below 18 years with open growth plates

• Bone pain or skeletal deformity

• Delayed growth or delayed motor development

• Clinical signs of rickets (e.g. wrist widening, bow legs, rachitic rosary)

Laboratory findings

Typical findings include:

• Low serum 25-hydroxyvitamin D (<20 ng/mL [<50 nmol/L]) in nutritional vitamin D deficiency

• Elevated alkaline phosphatase

• Low or normal serum calcium

• Low serum phosphate

• Elevated parathyroid hormone (secondary hyperparathyroidism)

Radiological findings

Plain radiographs of the wrist or knee typically demonstrate:

• Widened growth plates

• Metaphyseal cupping

• Metaphyseal fraying

• Metaphyseal splaying

• Generalized osteopenia

Investigations

• Serum 25-hydroxyvitamin D

• Serum calcium

• Serum phosphate

• Serum alkaline phosphatase

• Parathyroid hormone (PTH)

• Renal function tests

• Liver function tests

• Serum magnesium (when indicated)

• Urinary calcium and phosphate (selected patients)

• Plain X-rays of wrists and knees

• Genetic testing in suspected hereditary rickets

Non-pharmacological treatment

• Adequate sunlight exposure while avoiding sunburn

• Diet rich in calcium and vitamin D

• Nutritional counselling

• Encourage age-appropriate physical activity

• Management of underlying disorders

• Physiotherapy for muscle weakness

• Orthopaedic assessment for severe skeletal deformities

• Regular growth monitoring

Pharmacological treatment

Nutritional vitamin D deficiency

Infants (<12 months)

D: Colecalciferol (PO) 2,000 IU once daily for 6 weeks

OR

50,000 IU once weekly for 6 weeks

THEN

Maintenance therapy of 400 IU daily.

Children (1–18 years)

D: Colecalciferol (PO) 2,000 IU once daily for 6 weeks

OR

50,000 IU once weekly for 6 weeks

THEN

Maintenance therapy of 600–1,000 IU once daily.

Calcium supplementation

Children with inadequate dietary calcium intake should receive:

B: Calcium carbonate providing elemental calcium 500–1,000 mg/day orally in divided doses (dose adjusted according to age and dietary intake).

Monitoring

Reassess after 6–12 weeks with:

• Clinical improvement

• Growth assessment

• Serum calcium

• Serum phosphate

• Alkaline phosphatase

• Serum 25-hydroxyvitamin D

• Repeat radiographs if clinically indicated

Surgical management

Surgery is not routinely required.

Orthopaedic intervention may be indicated for:

• Persistent severe angular deformities after medical treatment

• Progressive deformity despite correction of vitamin D deficiency

• Pathological fractures requiring fixation

Procedures may include:

• Guided growth (hemiepiphysiodesis)

• Corrective osteotomy

• Internal fixation of fractures when indicated

Prevention

• Vitamin D supplementation during infancy according to national recommendations

• Adequate dietary calcium intake

• Safe sunlight exposure

• Maternal vitamin D sufficiency during pregnancy

• Routine supplementation for high-risk children

Prognosis

Nutritional rickets has an excellent prognosis when diagnosed and treated early. Biochemical abnormalities usually improve within weeks, while radiographic healing occurs over several months. Growth and skeletal deformities may completely resolve in young children, although severe or prolonged disease can result in permanent deformities requiring orthopaedic correction.