Overview
Osteomalacia and rickets are metabolic bone disorders characterized by defective mineralization of osteoid. The underlying problem is inadequate deposition of calcium and phosphate into the bone matrix, resulting in soft and structurally weak bones.
The condition is termed rickets when it occurs in children with open growth plates, and osteomalacia when it occurs in adults after epiphyseal closure. Although both conditions share similar biochemical abnormalities, the skeletal manifestations differ because rickets affects the growing skeleton whereas osteomalacia affects mature bone.
Pathophysiology
Normal bone mineralization requires adequate calcium and phosphate levels along with appropriate vitamin D activity. Vitamin D promotes intestinal absorption of calcium and phosphate and supports mineral deposition in osteoid.
When vitamin D deficiency or phosphate deficiency occurs, osteoid formation continues but mineralization fails. As a result, the bone matrix remains soft and mechanically weak. This leads to skeletal deformities in children and bone pain with fractures in adults.
- Defective mineralization of osteoid
- Accumulation of unmineralized bone matrix
- Decreased bone strength
- Increased fracture risk
Etiology
Multiple causes may lead to osteomalacia and rickets. The most common cause worldwide is vitamin D deficiency.
| Category | Examples |
|---|---|
| Vitamin D deficiency | Poor nutrition, lack of sunlight |
| Malabsorption | Celiac disease, inflammatory bowel disease |
| Renal disease | Renal osteodystrophy |
| Genetic disorders | Vitamin D–dependent rickets |
| Phosphate deficiency | X-linked hypophosphatemic rickets |
Clinical Features
Clinical manifestations depend on the age of the patient and severity of mineralization defect.
Features in Children (Rickets)
- Bowing of legs (genu varum or valgum)
- Delayed growth
- Rachitic rosary at costochondral junction
- Frontal bossing
- Widened wrists and ankles
Features in Adults (Osteomalacia)
- Diffuse bone pain
- Muscle weakness
- Difficulty walking
- Fragility fractures
- Pseudofractures (Looser zones)
Radiographic Features
Radiographic findings differ between rickets and osteomalacia because rickets involves abnormalities of the growth plate.
| Finding | Description |
|---|---|
| Metaphyseal cupping | Concave deformity of metaphysis |
| Metaphyseal fraying | Irregular metaphyseal margin |
| Widened growth plate | Due to impaired mineralization |
| Looser zones | Pseudofractures seen in osteomalacia |
Laboratory Findings
Laboratory investigations help confirm the diagnosis and determine the underlying cause.
| Test | Typical Finding |
|---|---|
| Serum calcium | Low or normal |
| Serum phosphate | Low |
| Alkaline phosphatase | Elevated |
| Vitamin D levels | Low |
Management
Treatment focuses on correcting the underlying metabolic abnormality and preventing skeletal deformities.
- Vitamin D supplementation
- Calcium supplementation
- Correction of phosphate deficiency
- Treatment of underlying renal disease
Orthopaedic treatment may be required for severe deformities. Surgical correction using osteotomy may be indicated in advanced cases with persistent deformity.
Orthopaedic Complications
- Long bone deformities
- Pathological fractures
- Growth disturbances
- Gait abnormalities
Key Exam Points
- Rickets occurs in children with open physes
- Osteomalacia occurs in adults
- Vitamin D deficiency is the most common cause
- Metaphyseal cupping and fraying are classic radiographic findings
- Looser zones represent pseudofractures in osteomalacia
- Treatment involves vitamin D and calcium supplementation