Metabolic Bone Disease Flashcards
What is osteomalacia?
Severe nutritional Vitamin D or calcium deficiency, causing insufficient mineralisation and ‘soft’ bones
What is vitamin D’s role in bone mineralisation?
Vitamin D stimulates the absorption of calcium and phosphate from the gut, calcium and phosphate then become available for bone mineralisation
What group is osteomalacia/Ricket’s most common in?
Children and elderly
When is the condition known as Rickett’s as opposed to Osteomalacia?
Rickets in a growing child and osteomalacia in the adult when the epiphyseal lines are closed
What causes osteomalacia?
Vitamin D deficiency
- Malabsorption
- Diet
- Lack of sunlight
Chronic pancreatitis
Chronic renal failure, as unable to hydroxylate vitamin D
Liver disease
Drug induced/anti-convulsants
How does Ricket’s present?
Growth retardation
Apathy/Irritability
Hypotonia
Deformities
- Wide joints
- Odd shaped ribs
- Persistent fontanelles/Large forehead
- Oddly curved spine
- Bow legged
How does osteomalacia present?
Bone pain/tenderness
Muscle weakness and aches
Proximal myopathy/waddling gait
Pathological fractures
What investigations are used in osteomalacia diagnosis?
Decreased serum 25-hydroxyvitamin D
Decreased Ca2+
Decreased phosphate
Increased PTH
Increased ALKP
Bone Biopsy
Xray
- Looser zones
- Osteopenia/radioluscent bone
DEXA scan, shows low bone mineral density
What are looser zones?
Thin band representing pseudo-fracture/fragility fractures
How is osteomalacia managed?
Vitamin D supplementation/colecalciferol
- 50,000 IU once weekly for 6 weeks
- 20,000 IU twice weekly for 7 weeks
- 4000 IU daily for 10 weeks
- Maintenance supplementary dose 800 IU or more per day should be continued for life after the initial treatment
What is Paget’s disease?
Chronic condition characterised by increased and disordered localised bone turnover
Describe the pathophysiology of Paget’s
Increased bone resorption (bone break down) followed by increased bone formation
Leads to structurally disorganised weaker bone
- Bigger
- Less compact
- More vascular
- More susceptible to deformity and fracture
What sex is more likely to be affected by Paget’s?
M>F
What age group is more likely to be affected by Paget’s?
>70s
Give risk factors for Paget’s
FH
Male
>Age
Northern latitude
How does Paget’s present?
Asymptomatic in 70% of cases, so most common finding is elevated ALKP
Bone deformity or fracture
- Large skull and bowing of legs
Excessive heat
Deep boring bone pain or due to impingement on nerves
Neurological complications
- Hearing loss due to compression of vestibulocochlear nerve
Rare development of osteosarcoma in affected bone
Which bones are most commonly affected by Paget’s?
Pelvis
Lumbar spine
Femur/long bones of the extremities
Skull
What investigations are used in diagnosis of Paget’s?
Isolated elevated ALKP
- Marker of osteoblastic activity
Normal Ca+ and Phosphate (PO4)
Xray
Bone biopsy, to exclude other conditions
What Paget’s signs are seen on X-Ray?
Thickened bone/dense areas
Lytic lesions/destruction of area of bone
How is Paget’s managed?
If asymptomatic, do not treat unless in skull or area requiring surgical intervention
Analgesia if pain
IV Bisphosphonate therapy, slows down bone lysis so move on to this if analgesia is not sufficient
One off IV zoledronic acid
Surgery
What surgical methods can be used in Paget’s management?
Correct bone deformities
Decompress impinged nerve
Give complications of Paget’s
Osteoarthritis if developing at a joint
Osteosarcoma
High output cardiac failure
Hypercalcaemia
Secondary immobility
What is Osteogenesis Imperfecta?
Genetic disorder of absent/defective type 1 collagen characterised by fragile bones and fractures
How many types of OI are there?
28
Describe type 1 osteogenesis imperfecta
Milder form, when child starts to walk and can present in adults
Describe type 2 OI
Lethal by age 1
Describe type 3 OI
Progressive deforming with severe bone dysplasia and poor growth
Describe type 4 OI
Similar to type 1 but more severe
How does OI present?
Easy fracture, Main symptom
Growth deficiency
Defective tooth formation/Dentigenesis imperfecta
Hearing loss
Blue sclera
- Vitreous humour is blue, sclera is see through
Scoliosis
Barrel chest
Ligamentous laxity
- Chronic body pain due to loose ligaments resulting in hyper-flexibility
Easy bruising
Normal Ca, PTH, PO4, ALP
What score assesses the degree of ligamentous laxity?
The Beighton Score
How is OI managed?
Surgical, treats fractures
IV Bisphosphonates, to prevent fracture
Social and educational adaptations
Genetic counselling for parents and next generation
What is osteoporosis?
Metabolic bone disease characterised by reduction in bone density leading to enhanced fragility and a consequent increase in fracture risk
Describe the pathophysiology of osteoporosis
Breakdown of bone > Formation of bone = Porous bones (decreased bone density)
What is the function of osteoclasts?
Break down/reabsorb bone
What is the function of osteoblasts?
Produce new bone
What is the function of Ca2+ and phosphate?
Used to build bone
What is the function of PTH?
Tells body to break down bone to produce Ca2+ and phosphate
What is the function of vitamin D?
Absorbs Ca2+ from gut, more Ca2+ to build bone
What is the function of calcitonin?
Tells body to stop breaking down bone
Give risk factors for osteoporosis
Post-menopausal women
Reduced mobility and activity
Low BMI
RA
Alcohol and smoking
Medications
- Corticosteroids
- SSRIs
- PPIs
- Anti-epileptics
- Anti-oestrogens
Give causes of non primary osteoporosis
Endocrine
- Thyrotoxicosis
- Hyper and hypoparathyroidism
- Cushings
- Hyperprolactinaemia
- Hypopotituraism
Rheumatology
- Rheumatoid arthritis
- Ankylosing spondylitis
- Polymyalgia rheumatica
GI
- IBD
- PBC
- Hepatitis
- Cirrhosis
- Chronic pancreatitis
- Coeliac
- Malabsorption
How does osteoporosis present?
Asymptomatic
Pathological fractures
What investigations are used in osteoporosis diagnosis?
Normal Ca, ALKP, PO4 and PTH
FRAX tool to assess fracture risk over next 10 years
DEXA Bone Scanning, compares individual’s bone density to a healthy adult
X-ray spine, first line for suspected osteoporotic vertebral fracture
- De-mineralisation
What factors does FRAX take into account?
Age
Gender, higher in women
Bone Mineral Density, higher in low BMD
Glucocorticoid use
FH
Previous Fracture
Smoking
RA
Country specific
When is a patient referred for a DEXA scan?
Referral for DEXA bone scanning based on FRAX score of >10% fracture risk at any site over next 10 years
What does DEXA give?
T score
What is a normal T score?
>-1
What T score is suggestive of osteopenia?
-1.5 to -2.5
What T score is diagnostic of osteoporosis?
<-2.5
What lifestyle measures are used in osteoporosis management?
Activity and exercise
Maintain a healthy weight
Adequate calcium intake
Adequate vitamin D
Avoiding falls
Stop smoking
Reduce alcohol consumption
What are the most commonly affected vertebrae in osteoporosis?
T7-T8 and T12-L1
What is the management of osteoporosis?
Biphosphonates
HRT
Risedronate
Denosumab/monoclonal antibody, use if unable to tolerate biphosphonates
Raloxifene/SERM
What are the requirements for bisphosphonates?
Adequate renal function required
Adequate calcium and vitamin D status required
Good dental health and hygiene advised
If over 75 and fragility fracture or long term steroid use, initiate without DEXA scan results
What is the mode of action of bisphosphonates?
Inhibits osteoclasts
Give examples of bisphosphonates
Alendronate
Risedronate
Etidronate
Give side effects of bisphosphonates
GORD/GI upset, switch to risedronate
Atypical stress fractures of femoral shaft
Osteonecrosis of the jaw
Hypocalcaemia
Requires drug holiday 1-2 years after 10 years on oral bisphosphonates
What is the follow up management of osteoporosis?
Low-risk patients not being put on treatment should be given lifestyle advice and followed up within 5 years for a repeat assessment
Patients on bisphosphonates should have a repeat FRAX and DEXA scan after 3-5 years
Treatment holiday should be considered if their BMD has improved and they have not suffered any fragility fractures. This involves a break from treatment of 18 months to 3 years before repeating the assessment.
How should biphosphonates be given?
Take at least 30 minutes before breakfast with water and sit upright for 30 minutes following
