Metabolic bone disease Flashcards
Osteoclasts and progenitor cell
bone resorption
myeloid
osteoblasts and progenitor cell
bone formation
mesenchymal
Pagets disease
increased bone resorption followed by increased bone formation
Describe how pagetic bone compares to normal bone
bigger, less compact, more vascular and more susceptible to fracture and deformity
what % of pagets is familial?
strong genetic component: 15-30%
Environmental and geographical - Paget’s
anglo-saxan
chronic viral infection in osteoclast
Symptoms of Paget’s disease
over 40's bone pain bone deformity? excessive heat over bone neurological complications eg nerve deafness
Most common presentation of Paget’s in 21st century
isolated elevation of serum alkaline phosphatase
presentation of pagets
bone pain and local heat
hearing loss
bone deformity or fracture
rarely osteosarcoma
Treatment of Paget’s
IV bisphosphonates - one off zoledronic acid infusion
Cause of rickets/osteomalacia
vit D or calcium deficiency leading to insufficient mineralisation
difference between osteomalacia and rickets
rickets in a growing child and osteomalacia when the growth plates have fused
What does vit D do for calcium and phosphate?
stimulates absorption from the gut
symptoms of osteomalacia
bone pain, muscle weakness and increased falls risk
Osteogenesis imperfecta
genetic disorder of connective tissue meaning the bones are fragile
Connective tissue affected in osteogenesis imperfecta
type 1 collagen
how many types of Osteogenesis imperfecta are there and which types are most common?
8
first 4
Type 1 Osteogenesis imperfecta
milder - when child starts to walk, can present in adults
Type 2 Osteogenesis imperfecta
lethal by age 1
type 3 Osteogenesis imperfecta
progressive deforming with severe bone dysplasia and poor growth
type 4 Osteogenesis imperfecta
similar to type 1 but more severe
Other features of Osteogenesis imperfecta
growth deficiency - hearing loss - defective tooth formation - blue sclera - ligamentous laxity - scoliosis - easy bruising
The brighton score is for what?
Osteogenesis imperfecta
describe the brighton score
1 point for each thumb touching wrist, each finger more than 90 degrees, each elbow more than 10 degrees, each knee more than 10 degrees and touch floor with straight legs
4 management principles of Osteogenesis imperfecta
surgery - treat fractures
medical - IV bisphosphonates
social - education and adaptions
genetic counselling
Osteoporosis
low bone mass, microarchitectural degeneration and increased bone fragility and fracture risk
FRAX
fracture risk assessment - age, BMD, falls etc
What does DXA stand for?
dual energy x-ray absorptiometry
Endocrine causes of osteoporosis
thyrotoxicosis hypo/hyper parathyroidism hypopituitarism low sex levels cushings hyperprolactinaemia
rheumatic causes of osteoporosis
RA, ankylosing spondylitis, polymyalgia rheumatica
GI causes of osteoporosis
inflammatory - UC and crohn’s
liver disease - PBC, cirrhosis, Hep C
malabsorption - coeliac, CF, ischaemic bowel
6 medications which cause osteoporosis
PPI steroids GnRH inhibitors aromatase inhibitors warfarin enzyme inducing anti-epileptics
peak BMD
about 30
When does BMD start to decrease rapidly?
menopause
How do we prevent osteoporotic fractures?
minimise risk factors
ensure good calcium and vitamin D
falls prevention strategies
medications
Side effects of HRT
blood clots, breast cancer and heart disease and stroke
Example of selective oestrogen receptor modulator
raloxifene
Side effects of selective oestrogen receptor modulator
hot flushes, clotting risk and lack of hip protection
1st line for osteoporosis
oral bisphosphonates
What are the requirements of the individual for oral bisphosphonates in osteoporosis?
renal function, vit D and calcium - adequate
good dental hygiene
SE of oral bisphosphonates
oesophagitis - iritis/uveitis - eGFR <30ml/min - atypical femoral shaft fractures
Denosumab
monoclonal ab against RANKL
How does denosumab work?
osteoclast formation function and survival inhibited
reduce osteoclatic bone resorption
How is denosumab administered?
subcut injection every 6 months
Side effects of denosumab
allergy/rash, symptomatic hypocalcaemia if vit D deplete,? ONJ, atypical femoral shaft fractures
What is teriparatide?
intermittent human parathyroid hormone
Disadvantages of teriparatide
injection site irritation - allergy - ? hypercalcaemia - cost