Clinical Biochemistry Flashcards
Biochemical markers for muscle damage?
Creatine kinase Lactate dehydrogenase Myoglobin AST Troponin
Myotonia?
Inability of muscle to relax after contraction
Rhabdomyolysis?
Breakdown of muscle fibres with increased CL
Dystrophy?
Is progressive abnormality
Causes of increased CK?
X 10 more upper limit of normal- MI, duchenne muscular dystrophy, rhabdomyolysis, polymyositis
X5-10- post surgery, trauma, sever exercise, grand mal convulsion, myosotis, carriers of duchenne muscular dystrophy
X5- physiological, hypothyroidism and drugs (statins, 1 in 10,000)
Rhabdomyolysis results in release of?
Myoglobin and other muscle proteins and intracellular ions into circulation
Skeletal muscle contribute to what percent of body weight?
40
Causes of rhambdomyolysis?
Severe exercise Injury Ischaemia Metabolic: McArdles disease, Malignant Hyperpyrexia, hypokalaemia, hypophosphatemia Infection Toxin Drugs
Rhambdomyolysis serum shows?
Hyperkalaemia Hyper phosphatemia Hyperuricaemia Hypocalcaemia Rise in creatinine Metabolic acidosis CK> x 10 ULN Urine dip positive for activity of myoglobin
Renal failure in rhabdomyolysis caused by?
Hypovolaemia hyperuricaemia
Aciduria- causes myoglobin to convert to ferrihaemate (nephrotoxic and it precipitates)
Metabolic acidosis hypovol
Dehydration increases urine conc and tubular obstruction by myoglobin casts Uris acid casts
Renal protection in rhabdomyolysis?
Give fluids,
Less common-
Mannitol- osmotic diuretic
Urine alkalinasation because most casts are produced in acid urine
Early hemofiltration
Biochemical investigations of muscle disease?
Plasma sodium, potassium, chloride etc
Plasma creatine kinase activity
ALT/AST (ALT increases in muscle disease)
Myoglobin in urine
Fatty acids, carnitine
Metabolic muscle disease?
1, carbohydrate metabolism
- Respiratory chain
- Fatty acid oxidation
Symptoms of metabolic muscle disease?
Most in early life Exercise intolerance mild to fatal Muscle pain after exercise Cramps Muscle damage Rhabdomyolysis Proximal muscle weakness Hypotonia Other organs affected Myoglobinuria
Carbohydrate metabolism muscledisorders signs and examples?
Cardiomegaly Hepatomegaly Macroglossia Respiratory dysfunction Progressive weakness with atrophy
E.g glycogen storage disease McArdle
Pompe
Defects of respiratory chain signs?
Cardiomyopathy, muscle weakness, exercise intolerance, hearing loss, seizures, ataxia, pigmentary retinopathy
E.g MELAS- maternal inheritance
Merrf, kearns sayre
Defects of fatty acid oxidation, lipid storage disease symptoms signs?
Muscle weakness and pain, myoglobinuria exercise intolerance symptoms present after prolonged period of exercise
Duchenne muscular dystrophy?
Dystrophin gene x linked recessive
Proximal weakness, gowers sign, hypertrophy, contractures
Lab results for duchenne muscular dystrophy?
Very high CK
Myasthenia gravis is due to?
Antibodies to AchR
Signs of myasthenia gravis?
Diplopia and ptosis
Who does myasthenia gravis occur in?
Young women, those with thymoma
Lambert Eaton myasthenic syndrome?
Antibodies against presynaptic voltage gated calcium channels
Can’t release acetylcholine
Rare
DMARDS methotrexate?
PIIINP type III pro collagen peptide, marker of liver fibrosis, indicates if you needs liver biopsy for those on long term methotrexate
Azathioprine?
Thiopurine methyl transferase transfers into inactive products, make sure If TMPT levels are low that you use a lower dose of drug
Bone turnover markers?
Osteolysis- serum CTX and urinary NTX
Osteogenesis- ALP and P1NP
Indicator of bone resorption?
CTX c-telopeptide of type 1 collagen
Indicator of bone formation?
PINP- n-propeptide of type 1 collagen
Gout affects how many adults?
1%
Secondary causes of gout?
Hypothyroidism, hyperparathyroidism,, aspirin, renal impairment, thiazides diuretics
What happens to solubility of Uric crystals?
Low pH and low temp and affected by concentration of other ions
First line treatment of gout?
Allopurinol, stops xanthine oxidase which converts to xanthine to uric acid
Probenecid and sulphinpyrazone to control gout?
Increase secretion of uric acid in kidneys
Osteomalacia?
Incomplete mineralisation as Ostiod is laid down
Rickets causes?
Widened growth plate and widened metaphysis
Osteomalacia causes?
Vit d deficiency
Abnormal vit d metabolism
Low phosphate - low intake/ excess losses
Signs of osteomalacia
Malaise, bone pain, proximal muscle weakness, myopathy
Clinical values for osteomalacia?
All phosphates high, ca low/ normal, phosphate low/normal
Looser zones in x rays
Rickets type 1 has?
Low 1,25 d- active form, due to renal failure
Rickets type 2?
Have 1,25 d but no receptor for it
Pagets disease?
Focal disorder of bone remodelling, accelerated bone turnover, increased osteoclast, weakened disorganised enlarged
Features of pagets?
Raised ALP , bone pain, bone enlargement, fractures etc
Kocher debre semelaigne syndrome?
Untreated hypothyroidism
