Osteomalacia and Rickets
Definition
Osteomalacia: defective mineralisation of existing bone matrix (osteoid) in adults or children.
Rickets: defective mineralisation of newly formed bone at the growth plate in children before growth plate closure.
Causes and Risk Factors
Osteomalacia and rickets share the same causes.
Most common: vitamin D deficiency [Ref]
- See the Vitamin D Deficiency article for causes and risk factors for vitamin D deficiency
Rarer causes: [Ref]
- Disorders of vitamin D metabolism (e.g. 1 alpha-hydroxylase deficiency, vitamin D receptor mutation)
- Disorders of phosphate metabolism (e.g. X-linked hypophosphataemia – due to increased FGF23 activity)
Clinical Features
Osteomalacia and rickets have distinctive clinical presentations.
Osteomalacia
Can occur in both adults and children
- Bone pain and tenderness (tend to be diffuse)
- Proximal myopathy
- Difficulty walking
- Waddling gait
- Increased risk of falls
Severe disease can result in:
- Pathological fractures
- Bone deformity (e.g. bowing of lower limbs)
Rickets
Only occurs in children (before growth plates have fused)
- Impaired growth – not always present
- Short stature
- Delayed walking
- Bone deformities
- Bowing of the legs
- Genu varum (more common than genu valgum)
- Swelling of the wrists, knees, and ankles (from bone-cartilage junction distension)
- Harrison groove – horizontal depression on the lower edge of the chest (at the attachment point of the diaphragm)
Neonatal presentation: [Ref]
- Late closing of fontanelles and soft skull (craniotabes)
- Poor feeding
- Irritability
- Hypocalcaemic seizures
Investigation and Diagnosis
Blood Tests
Typical biochemical changes (for both osteomalacia and rickets): [Ref1][Ref2]
- ↑ PTH
- ↑ ALP
- ↓ 25-hydroxyvitamin D
- ↓ Calcium ↓ Phosphate (but maybe normal in early disease / mild disease)
Be aware that the test of choice for vitamin D deficiency is serum 25-hydroxyvitamin D, the major circulating form of vitamin D. See the Vitamin D Deficiency article for more information.
Imaging
| Condition | Typical imaging findings |
|---|---|
| Osteomalacia [Ref1][Ref2] |
|
| Rickets [Ref1][Ref2] |
|
Management
For nutritional deficiency osteomalacia / rickets → ensure adequate vitamin D and calcium [Ref1][Ref2]
- Age-appropriate dose of vitamin D
- Ensure adequate dietary calcium intake
- Give supplementation if insufficient
See the Vitamin D Deficiency article for more information.