Metabolic bone disease Flashcards
What are osteoblasts
What are osteoclasts
How does the bone turnover cycle work?
Osteoblast-form new bone tissue where it is needed most
Osteoclast-cells that degrade bone to initiate normal bone remodelling and mediate bone loss in pathologic conditions
resorption- during which osteoclasts digest old bone; reversal- when mononuclear cells appear on the bone surface
formation- when osteoblasts lay down new bone until the resorbed bone is completely replaced
Why is vitamin D important for bones?
How is vitamin D synthesised
It helps bones absorb calcium, essential for bone turnover
Vitamin D absorbed through skin as 7DHC
Liver 25(OH) Vit D
Kidney 1,25(OH)2 Vit D
What is Paget’s disease of the bone
Localised disorder of bone turnover, mainly in the long bones and the skull. Increased bone resorption followed by increased bone turnover
Leads to disorganised bone, bigger, less compact, more vascular and more susceptible to deformity and fracture
What factors cause Paget’s disease?
Strong genetic component
15-30% are familial
Loci of SQSTMI
Restricted geographic distribution:those of anglo-saxon origins
Environmental trigger (chronic viral infection)
what are the symptoms of paget’s disease
Present in a patient 40 years with bone pain
Occasionally presents with bone deformity
Excessive heat over the pagetic bone
May present with neurological complications such as nerve deafness
What are the clinical symptoms of Paget’s disease
Isolated elevation of serum alkaline phosphatase, commonest presentation in the 21st century
Bone pain and local heat
Bone deformity or fracture
Hearing loss
Rare development of osteosarcoma in the affected bone
How should pagets disease be treated?
No evidence to treat asymptomatic Paget’s unless in skull area requiring surgical intevention
Should not be treated on alkaline phosphatase levels alone
IV bisphphosphatase therapy, one off IV zoledronic acid
What causes rickets and osteomalacia
Severe nutritional Vitamin D or calcium deficiency leading to insufficient mineralisation. In growing children this leads to rickets and in adults osteomalacia as the epiphyseal lines are closed.
How does rickets present in children?
Leads to stunded growth, wide bendy bones, large abdomen, big radial tubercle.
How does osteomalacia present?
Diffuse joint and bone pain (especially of spine, pelvis, and legs)
Muscle weakness.
Difficulty walking, often with waddling gait.
Hypocalcemia (positive Chvostek sign)
Compressed vertebrae and diminished stature.
Pelvic flattening.
Weak, soft bones.
Easy fracturing
What is osteogenesis imperfecta?
Brittle bone disease, it is a genetic disorder of the connective tissue characterised by fragile bones from mild trauma and even acts of daily life. Defects in type q collagen
What are the four most common types of osteogenesis imperfecta?
Type 1- milder form when child starts to walk, 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 osteogenis imperfecta
Growth deficiency Defective tooth formation Hearing loss Blue sclera Scoliosis Barrel chest Ligamentous laxity Easy bruising
How do you manage OI
Surgical-treat fractures
Medical- prevent fractures, intravenous bisphosphates
Social- adaptations educationally and socially
Genetic- genetic counselling for parents
