Musculoskeletal Pathology

Question 1

non neoplastic msk conditions

Answer 1

connective tissue diseases
metabolic diseases
fractures
degenerative diseases

Question 2

connective tissue disorders

Answer 2

autoimmune conditions
inflammatory diseases characterised by the presence of autoantibodies
often present with MSK symptoms/signs

Question 3

how can autoimmune disorders be diagnosed

Answer 3

by their autoantibodies

some conditions have a strong association with autoantibodies whereas some do not

Question 4

what is Rheumatoid arthritis

Answer 4

inflammation of joints 
autoimmune basis 
-rheumatoic factor 
-auto antibodies agains Fc IgE 
can ne systemic - absence of joint disease - many manifestations

Question 5

histology of rheumatoid arthritis

Answer 5

lots of plasma cells

lots of inflammatory cells

Question 6

what is pannus

Answer 6

inflammatory granulation tissue formed in the acute phase of rheumatoid arthritis

associated with destructive changes in the joint

Question 7

what happens in acute phase of rheumatoid arthritic

Answer 7

pannus formation

hyper plastic/reactive synovial

Question 8

chronic rheumatoid arthritis

Answer 8

cartilage is destroyed causing loss of joint space

fibrosis, deformity

Question 9

SLE (systemic lupus)

Answer 9

systemic autoimmune condition

autoantibodies are directed at structural parts of DNA

Question 10

two main autoantibodies found in SLE

Answer 10

ANA

anti double stranded DNA

Question 11

acute features of inflammatory arthrides

Answer 11

odema, fibrin, reactive features in synovial cells

Question 12

3 metabolic bone diseases

Answer 12

pagets (cellular remodelling and deformity of bones) 
osteomalacia (vit D metabolism abnormalities causing bone softening)
crystal arthropathies (accumulation of crystals in joints)

Question 13

An example of crystal arthropathy

Answer 13

gout

Question 14

what is gout

Answer 14

ureate crystals in joint space

Question 15

what is pseudo gout

Answer 15

calcium pyrophosphate crystals in joint space

Question 16

how are ureate crystals formed

Answer 16

uric acid is the end product of purine synthesis
adenine and guanine are purine based
therefore ureate is formed in DNA replication

Question 17

What is hyperuricaemia

Answer 17

increased production or reduced excretion of ureate

Question 18

what causes hyperuricaemia

Answer 18

usually idiopathic 
sometimes enzyme defect -HGPRT
Increased cell turn over 
-psoriasis 
-cancer (tumour lysis following chemo)

Question 19

what is the most common cause of gout

Answer 19

under excretion of ureate

often a drug side affects (thiazide diuretics)

Question 20

how do the ureate crystals end up in the joints

Answer 20

precipitation of crystals due to reduce solubility of ureate
unclear how they end up in joints

Question 21

clinical manifestations of gout

Answer 21

cause secondary degenerative changes in joint
deposition in soft tissue
renal disease

Question 22

what are the pathological findings in gout/ investigation

Answer 22

cytology - joint fluid examined under cross polarised light to detect needle shaped crystals

Question 23

Histology of gout

Answer 23

amorphous eosinophilic debris and inflammation (giant cells)
crystals lost during tissue processing
looks similar to pryophosphate form

Question 24

what is pseudo gout

Answer 24

calcium pyrophosphate

usually seen in older individuals in the large joints

Question 25

pseudo gout symptoms

Answer 25

usually asymptomatic incidental finding on x-ray range of joint pain, acute, chronic ect. crystals aren't distinct histologically

Question 26

what is Paget's disease

Answer 26

abnormality of bone turn over increase osteoclastic activity more bone but the bone isn't normally structured so patients develop fracture with minor trauma

Question 27

whats a cause/sign of pagets disease

Answer 27

alk phos levels high in isolation

Question 28

viral infections that can cause pagets disease

Answer 28

paramyxovirus, measles, RSV

Question 29

what are then 3 stages of pagets disease

Answer 29

osteolytic mixed burned out leads to thick excess bone with abnormal reversal lines- mosaic pattern

Question 30

signs of pagets disease

Answer 30

pain - micro fracture or nerve compression enlargement and abnormal shape of bones increased metabolism (heat, warm skin, AV shunt, high output heart failure) secondary malignancy -osteosarcoma

Question 31

what are the initial phases of a fracture

Answer 31

haematoma - fibrin mesh influx of inflam cells cytokine release after week 1- callus, organised haematoma, early recruitment and remodelling at ends of bone

Question 32

1-3 weeks after fracture

Answer 32

maximum girth of callus

Question 33

causes for delayed fracture healing

Answer 33

poor blood supply poor nutrition too much movement too great a distance ect.

Question 34

causes of pathological fracture

Answer 34

osteoporosis tumours benign or malignant

Question 35

what is avascular necrosis

Answer 35

bone infarction accounts for 10% of hip replacements often asymptomatic until bone collapses

Question 36

causes for avascular necrosis

Answer 36

``` trauma alcohol dysbarism steroid injection sickle cell disease infection ```

Question 37

what does avascular necrosis look like

Answer 37

usually wedge shaped infarct, often subcortical | histology - creeping substitution - new bone growing over old bone, seen in healing phase

Question 38

example of degenerative joint disease e

Answer 38

osteoarthritis

Question 39

what causes degenerative joint disease

Answer 39

mechanical injury can be secondary if load if abnormally distributed, previous fracture or anatomical abnormality

Question 40

degenerative joint disease histologically

Answer 40

not smooth cartilage, vertical cracks, roughing and fibrillation of the joint surface sometimes subchondral cyst formation osteophytes