Overview
Osteomalacia is softening of the bones generally secondary to vitamin D deficiencies leading to incomplete mineralisation of bone.
In growing children, rickets is characterised by defective mineralisation of the growth plate cartilage leading to skeletal deformities and reduction of growth secondary to vitamin D deficiency and subsequent incomplete bone mineralisation.
Epidemiology
- Vitamin D deficiency is common in both children and adults
- Peak incidence of osteomalacia is 50-60 years
- Males and females are equally affected
Risk Factors & Associations
- Dark skin, especially in South Asian, African-Caribbean, and Middle-Eastern people
- Vitamin D deficiency is as high as 94% in otherwise healthy South Asian adults
- Family history of vitamin D deficiency
- Age >65
- Pregnancy
- Obesity
- Covering of the face and body
- Housebound/institutionalised patients
- Poverty
- Vegetarianism
- Alcoholism
- Living in a high altitude
Aetiology
- Most commonly due to insufficient exposure to sunlight and nutritional deficiency
- GI malabsorption:
- Stomach and bowel resections
- Cystic fibrosis
- Biliary disease
- Crohn’s disease
- Coeliac disease
- Liver disease
- Renal disease e.g. CKD
- Drugs: anticonvulsants, rifampicin, HAART and cholestyramine
Presentation
Overview
- Myalgia is the most common presenting complaint
- Bone pain
- Lethargy
- Fractures may be seen
- May be seen with mild trauma or movement
- Usually, long bone fractures are seen
Signs on Examination
- Proximal muscle weakness
- Muscle wasting associated with proximal muscle weakness
- Waddling gait if the bone pain/proximal muscle weakness is severe
Differential Diagnoses
Osteoporosis
- Asymptomatic until a fragility fracture develops
- Osteomalacia is painful at the onset
- Osteomalacia has a history of limited sunlight exposure etc.
- Osteoporosis: normal serum calcium, phosphate, ALP, vitamin D, and PTH
- Osteomalacia: increased ALP, low phosphate, low vitamin D, increased PTH due to secondary hyperparathyroidism
Paget’s disease of the bone
- Most patients are asymptomatic
- Paget’s disease of the bone: only ALP raised
- Osteomalacia: increased ALP, low phosphate, low vitamin D, increased PTH due to secondary hyperparathyroidism
Investigations
The first investigations involve looking at the patient’s bone profile:
- Serum calcium level:
- Normal or low
- Serum 25-hydroxyvitamin D (25-OH cholecalciferol) level:
- Low
- Serum phosphate level:
- Low
- Serum alkaline phosphatase:
- High
- Serum parathyroid hormone level (PTH):
- High
- Urea and electrolytes (U&Es):
- To screen for kidney disease
Radiology is not necessary for adults if the diagnosis is clear but may include:
- Bone x-rays:
- May show coarsened trabeculae, osteopenia, pseudofractures, and fractures
- Dual-energy X-ray absorptiometry (DEXA) scans:
- Shows low bone mineral density (BMD)
Management
- 1st line: Vitamin D and calcium supplementation
- Cholecalciferol and calcium carbonate is an example
- 2nd line: Vitamin D metabolite and calcium supplementation
- Calcitriol and calcium carbonate
- Used if first-line measures are ineffective or patients with renal disease
Monitoring
- Check the patient’s 25-hydroxyvitamin D levels 2-3 months after starting therapy
- If undergoing long-term treatment, patients should have annual monitoring for signs and symptoms of osteomalacia or over-treatment with vitamin D
- Patients taking calcitriol should be assessed every 3 months along with a baseline renal ultrasound to evaluate for nephrocalcinosis or nephrolithiasis.
Patient Advice
- Patients should get adequate outdoor sun exposure to their skin, ensuring the use of sunscreen and avoiding excess exposure
Complications
- Secondary hyperparathyroidism
- Insufficiency fractures or pseudofractures
Prognosis
- Depends on the underlying cause of vitamin D deficiency, but the outcome is generally very good
- Following treatment, some individuals need long-term lifestyle changes to maintain adequate vitamin D levels
