Flashcards in Metabolic Bone Disease Deck (62)
What are the 2 main cells of bone remodelling?
What type of cell do osteoblasts develop from?
Mesenchymal progenitor cell
What type of cell do osteoclasts develop from?
Myeloid progenitor cell
What is the role of osteoclasts?
What is the role of osteoblasts?
How do osteoblasts control osteoclasts?
-When stimulated they produce RANKL
-RANKL binds to pre-osteoclasts
-Activation of osteoclasts
What produces vitamin D?
Where is vitamin D stored?
Liver, fat and muscle
Where is vitamin D activated?
In what form is vitamin D found in the skin?
In what form is vitamin D found in the liver?
In what form is vitamin D stored in the kidney?
1,25(OH)2 vit D
What happens to PTH when extracellular calcium is reduced?
What is Paget's disease?
-Localised disorder of bone turnover
-Increased bone resorption followed by increased bone formation
What does Paget's disease lead to?
Disorganised bone: bigger, less compact, more vascular and mores susceptible to deformity and fracture
What is the aetiology of Paget's disease?
-Strong genetic component
-15-30% are familial
-Loci of SQSTMI
-Restricted geographic distribution: those of Anglo-Saxon origins
-Environmental trigger: Possibility of chronic viral infection within Osteoclast
How does Paget's disease present?
-Bony deformity (occasional)
-Excessive heat over Pagetic bone
-Neurological complications (such as nerve deafness)
How is Paget's investigated?
-Marked expansion of the bone
-Dense and lucid areas
-Most useful definitive test
Isolated elevation of serum alkaline phosphotase
What can rarely develop from Paget's?
Osteosarcoma in the affected bone
How is Paget's disease treated?
-No evidence to treat asymptomatic Paget’s unless in skull or in area requiring surgical intervention.
-Do not treat based on a raised alkaline phosphatase alone
-Intravenous Bisphosphonate therapy-One off zoledronic acid infusion
What is the difference between rickets and osteomalacia?
-Rickets occurs in children before the epiphyseal plates fuse
-Osteomalacia occurs in adults after the epiphyseal plates fuse
What causes rickets/osteomalacia?
Severe nutritional vitamin D or Calcium deficiency causes insufficient mineralisation and thus Rickets in a growing child and Osteomalacia in the adult when the epiphyseal lines are closed
What does vitamin D do?
Stimulates the absorption of calcium and phosphate from the gut and calcium and phosphate then become available for bone mineralisation
What effect doe low vitamin D have on muscle function?
How does Rickets present in infants?
-Bandy legs (once they start walking)
-Large head (due to failure of fontanelles to close)
-Nodules on sides of ribs
-Failure to thrive
What are the symptoms of osteomalacia?
-Increased falls risk
What develops in osteomalacia?
What is osteogenesis imperfecta?
-Genetic disorder of connective tissue characterised by fragile bones from mild trauma and even acts of daily life
-Other non bone clinical features
-Broad clinical spectrum
What is the cause of OI?
Defects in type I collagent (There are 8 types of OI in total with 1 to 4 being the most common)