Metabolic Bone Disease Flashcards
What are the roles of osteoblasts and osteoclasts?
In healthy bone, osteoblasts absorb old bone and osteoclasts enter the hollow made by the osteoblasts and replaces it with new bone
What are the pathological processes behind Paget’s disease?
Disease of bone cell turnover that is localised to long bones and skull
Paget’s is a result of increased bone absorption that is followed by increased bone formation
This leads to bone that is bigger, less compact, more vascular and more susceptible to deformity and fracture
What percentage of cases of Paget’s disease have a clear family history?
15-30%
What is the affected gene in Paget’s disease?
SQSTMI
What are the causes of Paget’s disease?
Genetic predisposition- people of Anglo-saxon origin, high incidence Irish emigration countries
Environmental factors- chronic infections (decline in incidence since implementation of childhood vaccination)
What are the characteristics of Paget’s disease?
- Symptoms present in a patient >40
- Bone pain that is constant without and exacerbating or alleviating factors
- Bone deformity
- Excessive heat over the Pagetic bone
- Neurological complications such as nerve deafness
What investigations should be done in suspected cases of Paget’s?
X-ray followed by isotope bone scan
What is the commonest presentation of Paget’s?
Isolated raised serum alkaline phosphatase
What is a possible complication of Paget’s disease?
Osteosarcoma of the affected bone
Describe the management of Paget’s disease?
If asymptomatic Paget’s or raised alkaline phosphatase alone then no treatment should be given
In symptomatic Paget’s or Paget’s affecting skull- IV bisphosphonate therapy with a single dose of IV zoledronic acid
Surgery can also be helpful but tricky due to highly vascularised bone
What is the difference between rickets and osteomalacia?
Same disease, rickets occurring before fusing of the epiphyseal plates and osteomalacia occurring after
What is the cause of rickets/osteomalacia?
Severe nutritional vitamin D or calcium deficiency
What are the characteristics of rickets?
- Failure to thrive
- Short stature
- Head appears large
- Bandy legs when they start walking
- Epiphyses flare so get nodular bits at wrists, ankles and ribs
When does bow-leggedness require surgical fixation?
If rickets caught and treated early enough then bow-leggedness will resolve spontaneously but if not then surgery will be required
What are the characteristics of osteomalacia?
- Common in elderly or institutionalised people
- Pain in joints and bones
- Aching
- Muscle dysfunctions
What is osteogenesis imperfecta?
Osteogenesis imperfecta is a genetic disorder of connective tissue that is characterised by fragile bones from mild trauma and even daily activities. There is a broad spectrum of disease from those who are prenatally fatal up to those who present in their 40s with early osteoporosis.
What are the four most common types of 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 and symptoms of osteogenesis imperfecta?
- Growth deficiency
- Defective tooth formation (dentigenesis imperfecta)
- Hearing loss
- Blue sclera
- Scoliosis
- Barrel chest
- Ligamentous laxity
- Easy bruising
How is osteogenesis imperfecta managed?
Surgically- treatment of fractures
Medically- IV bisphosphonates
Socially- education on lifestyle adaptations
Genetically- genetic counselling for parents and next generation
In what ages are fractures common in osteogenesis imperfecta?
Fractures common in up to 20 years of age, at which point incidence decreases until the elderly, when fractures are common again
What is osteoporosis?
Osteoporosis is the commonest metabolic bone disease in the developed world. It is a metabolic bone disease characterised by low bone mass and micro architecturial degeneration of bone tissue, leading to increased bone fragility and a consequent increase in fracture risk.
What are some common bone fractures in osteoporosis?
Wrist
Spine
Hip
What spinal deformity is common in osteoporosis?
Kyphosis
Describe how bone mass changes with age
Peak bone mass is reached in the late 20s and remains constant until the mid 40s, at which point bone mass begins to decrease. In males, bone mass decreases at around 1% per year. In females, bone density loss increases up to about 5% loss per year during and 5 years post menopause. Risk of fracture is dependent on age, bone mass density, falls and bone turnover.
What scoring system can be used to asses fracture risk and at what score should action be taken?
WHO FRAX scoring system
Assesses risk of fracture in next ten years, if risk >10% then refer for bone density scan
What scores are given in a bone density scan and what does each mean?
A T-score and a Z-score. A T-score is a comparative score based on someone of the same sex, race and body mass but at a younger age, where a Z-score is a comparative score based on someone of the same age, sex, race and body mass.
What are the endocrine causes of osteoporosis?
- Thyrotoxicosis
- Hyper and hypoparathyroidim
- Cushings
- Hyperprolactinaemia
- Hypopituitarism
- Early menopause
What are the rheumatic causes of osteoporosis?
- Rheumatoid arthritis
- Ankylosing spondylitis
- Polymyalgia rheumatica
What are the gastroenterological causes of osteoporosis?
- Inflammatory diseases: UC and crohns
- Liver diseases: PBC, CAH, Alcoholic cirrhosis, Viral cirrhosis( hep C)
- Malabsorption: chronic pancreatitis, coeliac disease, whipples disease, short gut syndromes and ischaemic bowel
What medications can cause osteoporosis?
- Steroids
- PPI
- Enzyme inducting antiepileptic medications
- Aromatase inhibitors
- GnRH inhibitors
- Warfarin
What steps should be taken to prevent osteoporotic fractures?
Identify and minimise risk factors
Ensuring good calcium and vitamin D levels
Falls prevention statuses
Medications
What medications can be used to manage osteoporosis?
Hormone replacement therapies Selective oestrogen receptor modulators (SERMs) Bisphosphonates Denosumab Teriparatide
What are the side effects of hormone replacement therapy?
- Increased risks of blood clots
- 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
Usually stopped by 60 in both sexes to avoid increased risk of breast or prostate cancer
What are the side effects of SERMs?
- Hot flushes if taken close to menopause
- Increased clotting risks
- Doesn’t prevent hip fracture
What are the contraindications for bisphosphonates?
eGFR of >30 required for oral bisphosphonates and >45 for IV
Adequate vitamin D and calcium status required
Good dental hygiene required
What are the side effects of bisphosphonates?
- Oesophagitis
- Iritis/uveitis
- Osteonecrosis of the jaw
- Atypical femoral shaft fractures- more common in Asian population, osteoporotic fractures do not usually occur in the shaft
What are the side effects of denosumab?
- Allergy/rash
- Symptomatic hypocalcaemia if given when vitamin D deplete
- Osteonecrosis of the jaw
- Atypical femoral shaft fractures
What are the side effects of teriparatide?
- Injection site irritation
- Rarely hypercalcaemia
- Allergy
- Cost
