Overview
Rickets
1. Clinical Overview
Summary
Rickets is defective mineralisation of the growth plate occurring in children before epiphyseal closure. It results from inadequate calcium/phosphate for bone mineralisation, most commonly due to vitamin D deficiency.
Key Facts
| Aspect | Detail |
|---|---|
| Definition | Defective mineralisation of growth plate cartilage |
| Most Common Cause | Vitamin D deficiency (nutritional rickets) |
| Peak Age | 3-18 months |
| Key Biochemistry | ↓Ca, ↓PO4, ↑ALP, ↑PTH, ↓Vit D |
| Key Radiology | Metaphyseal cupping, fraying, widening |
Clinical Pearls
- Rachitic Rosary: Beading at costochondral junctions - pathognomonic
- Craniotabes: Soft skull bones, "ping-pong ball" feel
- Not Just Bones: Remember cardiac and respiratory complications
- Treat Early: Delay leads to permanent skeletal deformities
2. Epidemiology
Risk Factors
| Risk Factor | Mechanism |
|---|---|
| Dark skin pigmentation | Reduced vitamin D synthesis |
| Limited sun exposure | Covered clothing, indoor lifestyle |
| Northern latitudes | Less UVB exposure |
| Exclusive breastfeeding | Breast milk low in vitamin D |
| Maternal deficiency | Inadequate transfer to fetus |
| Malabsorption | Coeliac, CF, short gut |
3. Pathophysiology
Vitamin D Metabolism
Sunlight (UVB) on Skin → Cholecalciferol (D3)
↓
LIVER (25-Hydroxylation)
↓
25(OH)D (Calcidiol) ← Measured
↓
KIDNEY (1α-Hydroxylation)
↓
1,25(OH)2D (Calcitriol) ← Active
↓
Intestinal Ca/PO4 Absorption
↓
Bone Mineralisation
Pathophysiology of Bone Changes
Vitamin D Deficiency → ↓Ca/PO4 Absorption → Hypocalcaemia → ↑PTH → Phosphate wasting → Defective mineralisation
4. Clinical Presentation
Classic Clinical Signs
| Sign | Description |
|---|---|
| Craniotabes | Soft skull bones |
| Frontal bossing | Prominent forehead |
| Rachitic rosary | Costochondral beading |
| Harrison's sulcus | Lower rib indentation |
| Widened wrists | Metaphyseal expansion |
| Genu varum | Bow legs (younger) |
| Genu valgum | Knock knees (older) |
Non-Skeletal Features
Hypotonia, delayed milestones
Common presentation.
Dilated cardiomyopathy
Common presentation.
Respiratory weakness
Common presentation.
Dental enamel hypoplasia
Common presentation.
Hypocalcaemic seizures
Common presentation.
5. Clinical Examination
| Area | Findings |
|---|---|
| Skull | Craniotabes, frontal bossing |
| Chest | Rachitic rosary, Harrison's sulcus |
| Limbs | Wrist widening, bowed legs |
| Height | Often below expected |
| Muscle | Hypotonia, weakness |
6. Investigations
Blood Tests
| Test | Finding |
|---|---|
| Calcium | Low or low-normal |
| Phosphate | LOW |
| ALP | HIGH |
| 25(OH)D | LOW (<25 nmol/L deficient) |
| PTH | HIGH |
Radiology
| Feature | Description |
|---|---|
| Metaphyseal cupping | Concave metaphysis |
| Fraying | Irregular, brush-like border |
| Widening | Expanded metaphysis |
| Osteopenia | Generalised demineralisation |
7. Management
Vitamin D Treatment
| Age | Daily Therapy |
|---|---|
| <6 months | 3,000 IU/day × 8-12 weeks |
| 6-12 months | 6,000 IU/day × 8-12 weeks |
| >1 year | 6,000 IU/day × 8-12 weeks |
Then: Maintenance 400-1000 IU/day
Additional Management
- Calcium supplementation if dietary intake low
- IV calcium if symptomatic hypocalcaemia
- Surgical correction (8-plates/osteotomy) for persistent deformity
8. Complications
| Complication | Notes |
|---|---|
| Permanent deformity | If not treated early |
| Short stature | Growth plate dysfunction |
| Hypocalcaemic seizures | Medical emergency |
| Dilated cardiomyopathy | Serious |
9. Prognosis & Outcomes
| Parameter | Expected |
|---|---|
| Biochemistry | ALP normalises 4-6 weeks |
| Radiological | Healing 3-6 months |
| Clinical | Catch-up growth 6-12 months |
Early treatment = excellent outcomes.
10. Evidence & Guidelines
| Organisation | Key Points |
|---|---|
| Global Consensus (2016) | 25(OH)D <30 nmol/L = deficient |
| RCPCH | 400 IU/day for all children |
11. Patient / Layperson Explanation
What is rickets? A bone condition when children don't get enough vitamin D or calcium, making bones soft and weak.
Prevention:
- Vitamin D drops from birth (400 units daily)
- Adequate calcium in diet
- Safe sun exposure
Treatment:
- Vitamin D supplements (high doses initially)
- Full recovery if caught early
12. References
- Munns CF, et al. Global Consensus on Nutritional Rickets. JCEM. 2016.
- RCPCH. Vitamin D supplementation. 2020.
- NICE. Vitamin D deficiency. PH56.