L7 - Clinical biochem MSK COPY

Question 1

MUSCLE DISEASE

i) what is the most widely used and sensitive biomarker or muscle damage? name three others
ii) define myalgia, myotonia, myositis, rhabdomyolysis and myopathy? which has a rise in CK? which does not?
iii) what is dystrophy?

Answer 1

i) creatine kinase is the most widely used
- also use LDH, AST and troponin

ii) myalgia - pain attributed to muscle with or without a rise in CK

myotonia - inability of a muscle to relax after contraction

myositis - inflam of muscle - often autoimmune

rhabdomyolysis - widespread breakdown of muscle fibres with raised CK

myopathy - non specific term used to describe muscle disorder

iii) dystrophy - progressive abnormality

Question 2

CAUSES OF INCREASED CK

i) what can cause >10x upper limit of normal? (3)
ii) what can cause 5-10 upper limit of normal? (2)
iii) what can be a cause of <5x upper limit of normal? (3)

Answer 2

i) x10 upper limit - polymyositis, rhabdomyolysis, DMD, MI
ii) 5-10 upper limit - post surgery, trauma, intense exercise, convulsions, DMD carrier
iii) <5 upper limit - physiological with big muscle bulk, hypothyroid, drugs eg statins

Question 3

RHABDOMYOLYSIS

i) what is it?
ii) what is released? what does this result in?
iii) name three causes
iv) what will CK be? will there be a acidosis or alkalosis?
v) how may the urine look?
vi) which organ may fail? what is therefore necessary in RML

Answer 3

i) rapid destruction of striated muscle
ii) release of myoglobin and other proteins/ions to the circulation
- can result in loss of water and electrolyte imbalance
iii) severe exercise, injury, ischaemia, metabolic

iv) CK > 10x upper limit
- metabolic acidosis

v) coca cola urine
vi) renal failure therefore protect the kidneys

Question 4

METABOLIC MUSCLE DISEASE

i) name three defects that can cause it? what does this lead to?
ii) do symptoms present early or late in life? what may the preson be intolerant to?
iii) give an example of a respiratory chain disorder
iv) is CK always elevated? when may abnormalities present?

Answer 4

i) disorders in carbohydrate metabolism, defects in respiratory chain and defects in fatty acid oxidation
ii) present early in life and may be exercise intolerant
iii) MELAS
iv) abnorms may only be seen in an attack - inc raised CK

Question 5

STRUCTURAL MUSCLE DISEASE

i) which disease has a very high CK?
ii) what would be requested in lambert eaton myaesthenic syndrome?

Answer 5

i) DMD
ii) VG calcium channel antibodies

Question 6

BIOCHEM IN RHEUMATOLOGY

i) name four things biochem may be used to monitor in rheumatology
ii) what is a marker of liver fibrosis? what drug may these be elevated in?
iii) what is the most common bone resorption marker? most common bone formation marker?

Answer 6

i) drug monitoring eg DMARDs, bone turnover markers, gout, vit D
ii) PIIINP is a marker of liver fibrosis > elevated in methotrexate use

iii) bone resorption - CTX
bone formation - P1NP

Question 7

PAGETS DISEASE

i) what is it a disorder of?
ii) name two things its characterised by?
iii) what may be raised in the blood?
iv) what is a differential dx

Answer 7

i) disorder of bone remodelling
ii) see accelerated bone turnover and increased osteoclast mediated resorption
iii) raised ALP
iv) gout is a differential