Pathology Flashcards
What does bone act as a reservoir for?
Calcium
Hypocalcaemia stimulates the parathyroid glands to produce ____1_____ which promotes _______2_______ As the serum calcium rises PTH production is ____3______
1) parathyroid hormone
2) bone resorption, calcium absorption from the gut and reabsorption of calcium from the kidney
3) switched off
Define arthritis
wide range of disorders causing pain and inflammation in joint
What is the most common disorder of joints?
Osteoarthritis
Describe the two groups of osteoarthritis
Secondary- clear association with some predisposing condition which may be virtually any abnormality of a joint e.g. injury or abnormal stresses. This type often affects a single joint.
Primary- no obvious predisposing cause but often runs in family. More generalised.
Describe early pathological changes in osteoarthritis
Chondrocytes are injured and proliferate replacing the specialised matrix resulting in the matrix becoming softer .
Then get flaking and fibrillation of the surface.
Describe later pathological changes in osteoarthritis
Cartilage is completely worn away – bone on bone
Subchondral cysts
Surface becomes “polished” – eburnation
Remodeling to cope with stress
Formation of osteophytes- outgrowth of irregular bone
Explain radiological appearance of osteoarthritis
Loss of joint space = Cartilage loss
Subchondral sclerosis = Eburnation
Subchondral cysts = Synovial fluid accumulation
Osteophytes = Disorganised bone remodelling
What is rheumatoid arthritis?
A common systemic chronic inflammatory disease that is auto-immune.
Early pathological changes of rheumatoid arthritis?
signs of inflammation and swelling over joints
swollen inflamed synovium
will see fibrinous exudate, villiform hyperplasia and intense infiltration with lymphocytes and plasma cells
Intermediate pathological changes of rheumatoid arthritis?
joints are swollen and marked muscle wasting
laxity (loose) of capsule and soft tissue inflammation in periarticular tissues.
Destructino of cartilage by enzymatic action and granulation tissue spreading over the articular surface (pannus- abnormal layer of granulation tissue)
What is pannus?
Abnormal layer of granulation tissue
Late pathological changes of rheumatoid arthritis?
Severely distorted joint and permanent deformity due to contracture and often subluxation
Inflammation is usually less marked- fibrous adhesions across the joint may be irregular bony union
Describe extra-articular manifestations of rheumatoid arthritis?
Loads- rheumatoid nodules big one
What are the seronegative spondyloarthritides
Group of rheumatological disorders with some common features:
ankylosing spondylitis
psoriatic arthritis
IBD arthritis
Ankylosing spondylitis is an arthritis affecting particularly the _____1______ but peripheral arthritis is also seen. `The disorder is like Rheumatoid arthritis but differs in that it causes ____2_____
1) sacroiliac, costovertebral and vertebral joints
2) osseous ankylosis (bony union) so that no movement of the affected joints is possible
Describe enteritis associated arthritis
Auto-immune associated reaction to infection or organisms with high LPS trigger an immune response causing the arthritis
Describe psoriatic arthritis
10% patients with psoriasis Predominantly affects joints of hands and feet 20% cases involve sacro-iliac joints Joint involvement may be asymmetrical DIP joints characteristically affected Similar histology to RA
Why is history and examination important when diagnosing an arthritis?
Histologically they all look almost the same
Describe infectious arthritis
Potentially destructive process
Suppurative
Haematogenous spread of organisms
S aureus in adults (H influenza in young children)
Gonococcal infection in young adults
Sickle cell predisposes to Salmonella arthritis
Typically involves single joint (knee most common)
Systemic features of infection
Acutely painful & swollen joint ; Aspirate purulent fluid
Mycobacterial, Lyme disease, Viral
What are the crystal arthropathies?
Crystal arthropathy is a class of joint disorder (called arthropathy) that is characterized by accumulation of tiny crystals in one or more joints.
Gout – urate metabolism
Pseudo-gout – calcium pyrophosphate
What two things do you need for gout?
Increased production of uric acid and decreased excretion
Causes of gout?
INCREASED PRODUCTION Usually idiopathic Unkown enzyme defect (90%) Known enzyme defect - HGPRT deficiency Lesch Nyhan syndrome – rare Impairs purine nucleotide salvage pathway Degraded to urate Increased cell turnover Psoriasis, Cancer and tumour lysis following chemotherapy
REDUCED EXCRETION Under- excretion A common cause of gout Chronic renal disease Drug side effect thiazide diuretics reduce urate excretion
Pathological findings of gout?
Cytology
Joint fluid examined under cross-polarized light to detect needle shaped crystals.
Histology (tophus)
Amorphous eosinophilic debris and inflammation (giant cells)
Crystals lost during tissue processing
NB – pyrophosphate arthropathy
Causes of pseudo gout?
Usually idiopathic
May be known cause – hypercalcaemia (inc. hyperparathyroidism), haemachromatosis, hypomagnesaemia, ochronsis, hypothyroidism
What will you see on X-ray in pseudo gout?
dense deposits
Pseudogout is often ______ and found incidentally on ______
asymptomatic
x-ray
What is osteoporosis characterised by?
Low bone mass
Microarchitectural deterioration of bone with an increase in bone fragility and susceptibility to fracture
Define osteoporosis and osteopenia?
Osteopenia 1-2.5 SD below mean peak bone mass
Osteoporosis >2.5 SD below mean peak bone mass
When does osteoporosis become more common?
It becomes more common with increasing age and is more common in women especially after menopause
When is peak bone mass?
Young adult hood (20s) thereafter bone mass decreases. A high peak bone mass makes osteoporosis less likely.
When would you get localised osteoporosis?
Commonly due to disuse and is seen as a complication of other disorders such as immobilisation following a fracture, limb paralysis adjacent to severe joint disease with limitation of movement.