Metabolic Bone Disease Flashcards
What causes Rickets and Osteomalacia?
What is the difference between the two?
Severe nutritional vitamin D deficiency causes insufficient mineralisation and thus rickets in a growing child and osteomalacia in the adult when the epiphyseal lines are closed
What are the signs of osteomalacia?
Soft spot on baby’s head is slow to close
“Bony necklace” of nodules around ribs
Curved bones
Big, lumpy joints
Bowed legs
What is Paget’s disease?
What goes wrong and what does it lead to?
Localised disorder of bone turnover
Increased bone resorption followed by increased bone formation
leads to disorganised bone: bigger, less compact, more vascular and more susceptible to deformity and fracture
What are the symptoms of Paget’s disease?
When does it present?
Presents in a patient >40 years with bone pain
Occasionally presents with bone deformity, excessive heat over the pagetic bone or by neurological complications (deafness)
Paget’s disease effecting the skull can lead to what?
Deafness
What is the genetic component of the aetiology of Paget’s disease?
How does this play into geographic distribution?
Strong genetic component
15-30% are familial
Restricted geographic distribution: those of Anglo-Saxon origins
Possibility of chronic viral infection within osteoclasts may lead to what?
Paget’s disease
What blood test will be elevated in the majority of Paget’s disease?
Alk Phos
May be an isolated elevation that is picked up by chance (should be looked into)
What may Paget’s present with on very rare occasions?
what very rare complication occurs in Paget’s
Osteosarcoma of affected bone
What is osteogenesis imperfecta?
broad definition
Genetic disorder of connective tissue characterised by fragile bones from mild trauma and even acts of daily life
How does osteogenesis imperfecta vary?
Why is this?
Broad clinical range due to 8 different defects in type 1 collagen
What are the 4 most common defects in type 1 collagen that occur in osteogenesis imperfecta?
Type 1:
- Milder form
- When child starts to walk and can present in adults
Type 2:
-Lethal by age 1
Type 3:
-Progressive deforming with severe bone dysplasia and poor growth
Type 4:
-Similar to type 1 but more severe
What are the signs of osteogenesis imperfecta?
Growth deficiency
Defective tooth formation
(dentigenesis imperfecta)
Hearing loss
Blue sclera
Scoliosis
Barrel chest
Ligamentous laxity
Easy bruising
How do you treat osteogenesis imperfecta?
Pins put in place in childhood
These support bone and grow with the bone as the child grows
What is the definition of osteoporosis?
Metabolic bone disease characterised by low bone mass and micro architectural deterioration of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk
What result on a DXA bone scan would define osteoporosis?
What is a low trauma fracture?
A fracture due to a force equivalent to a fall from standing height or less
You shouldnt break a bone when you fall over. Something is wrong with the bone if you do
What are the 3 classic fractures in osteoporosis?
Wrist, spine and hip
What low trauma fractures do not suggest osteoporosis?
(when seen these wouldnt make you worry about osteoporosis)?
Fingers/toes
Nose and Skull
What 6 things make people at risk of having thin bones?
Age
Genetic predisposition
Nutritional factors
-Low body weight and poor calcium and Vit D intakes
Immobility
Diseases which influence bone turnover:
- Thyrotoxicosis
- Malabsorption
- Inflammatory arthritis
Medications:
- Steroids
- Aromatase inhibitors
- Warfarin
- TCA
- Diabetic medications
- Anticonvulsant
How does bone mass change as we age?
As we grow bone mass increases
At around 20 we stop growing and reach peak bone mass at 30
Accelerated loss begins at menopause
Gradual loss in elderly
(this is all effected by the level of activity of osteoclasts and osteoblasts)
What 4 factors effect peak bone mass?
Genetic factors
Nutritional factors
Exercise (weights)
Influenced by disease processes and by drugs such as corticosteroids
What 5 factors effect age related bone loss?
Loss of sex hormones
Genetic factors
Nutritional factors
Exercise (weights)
Drugs such as corticosteroids and aromatase inhibitors
How do you measure bone mass?
DEXA scan
-Calculate bone mass along with T and Z score
What is T score and Z score?
T score:
- Compares bone mass to that of a younger person
- Same ethnicity and sex
Z score:
- Compares bone mass to peers
- Same age, ethnicity and sex
How do you use T-score to decide when to treat?
Give score and treatment
Normal (T score above -1)
- Reassure
- Lifestyle advice
Osteopenia (T score between -1 and -2.5)
- Lifestyle advice
- Treat if previous fracture
Osteoporosis (T score less than -2.5)
- Lifestyle advice
- Offer treatment
What is referral for DEXA scan dependent on?
how do clinicians decide when to do a DEXA scan?
Based on FRAX or QFracture score >10% fracture risk at any site over next 10 years
Name some independent risk factors for osteoporosis used in FRAX score
Prior fracture
Family history of fracture
Current smoking
Ever use of corticosteroids
Alcohol (3 or more units a day)
Rhaumatoid arthritis
What are some of the limitations of the FRAX score?
Not all known risk factors included:
-Falls, biochemical markers
Lacls detail on some risk factors:
-Dose of corticosteroids, smoking, prior fracture
Depends on adequacy of epidemiological information
Limited country models available
Model relevant only for untreated patients
Does not replace clinical judgment
What length of steroid use puts someone at risk of steroid induced osteoporosis?
3 or more months
What are the side effects of HRT treatment in osteoporosis?
Increased risk of clotting
Increased risk of breast cancer with extended use into late 50s/ early 60s
Increased risk of heart disease and stroke if used after large gap from menopause
What does SERM stand for?
Selective oEstrogen Receptor Modulator
Form of HRT used in osteoporosis which reduces the rates of vertebral fracture
(NO effect on non-vertebral fracture rates)
What are the side effects of SERMs?
Hot flushes if taken close to menopause
Increased clotting risks
Lack of protection at hip site
What are the main treatments for osteoporosis?
What do they do?
Bisphosphonates
Potent anti-resorptive agents
Name 3 bisphosphonates
Etidronate
Alendronate
Risedronate
What are the side effects of bisphosphonates?
Oesophagitis
Iritis/ uveitis
Osteonecrosis of the jaw (ONJ)
Atypical femoral shaft fractures
What is the mechanism of action of strontium ranelate in osteoporosis?
Strontium replaces calcium in bone
What are the side effects of strontium ranelate?
Increased clotting risks
Increased cardiovascular risks
Artificially elevates bone density and can cause misleading results on future DXA scans
What is teriparatide?
Intermittent Human Parathyroid hormone
Reduces fracture rates.
Really is a brilliant drug
What are the problems with teriparatide?
side effects etc
Injection site irritation
Rarely hypercalcaemia
Allergy
COST COST COST
What is Denosumab?
what does it do? how is it given? what is the advantage?
Monoclonal antibody against RANKL
Reduces osteoclastic bone resorption
Subcutaneous injection every 6 months
Safer in patients with significant renal impairment than bisphosphonates
What are the side effects of denosumab?
Allergy/ rash
Symptomatic hypocalcaemia if given when Vit D deplete
-Ca2+ can drop rapidly risking arrythmia
ONJ
Atypical femoral shaft fractures
