Crystal arthopathies and polymalgia rheumatic Flashcards
What are common crystal deposition diseases?
> Monosodium urate - gout
> Calcium pyrophosphate dihydrate (CPPD) - Pseudogout
> Basic calcium phosphate hydroxy-apatite (BCP) – calcific periarthritis/tendonitis
Which crystals are found in gout?
Monosodium urate
Monosodium urate crystals?
Gout
Which crystals are found in pseudogout?
Calcium pyrophosphate dihydrate (CPPD)
Which crystals are found in calcific periarthritis/tendonitits?
Basic calcium phosphate hydroxy-apatite (BCP)
Calcium pyrophosphate dihydrate (CPPD) crystals?
Pseudogout
Basic calcium phosphate hydroxy-apatite (BCP)?
Calcific periarthritis/tendonitis
What are typhus-tophi?
Massive accumulations of uric acid
What is the main contributor to the bodies rate pool?
> 2/3rds come from the production of uric acid when purines are degraded
> The rest comes from diet
How is uric acid excreted?
> 70% is excreted via the kidneys
> The rest is eliminated into the biliary tract
What is uric acid in the colon converted to?
Converted by colonic bacterial uricase to allantoin
What is the main cause of hyperuricaemia in gout usually?
Decreased efficiency of renal urate clearance
Where do purines come from?
> Diet
DNA/RNA
Recycled HGPRT (Hypoxanthine)
Why can alcohol increase the risk of gout?
> The metabolism of ethanol to acetylene CoA leads to adenine nucleotide degradation, resulting in increased formation of adenosine monophosphate, a precursor of uric acid.
> Alcohol also increases the lactic acid level in blood, which inhibits uric acid excretion
What can lead to hyperuricaemia - Overproduction?
Overproduction:
> Malignancy e.g lymphoproliferative, tumour lysis syndrome
> Severe exfoliative psoriasis
> Drugs e.g. ethanol, cytotoxic drugs
> Inborn errors of metabolism
> HGPRT deficiency
What can lead to hyperuricaemia - under excretion?
Under excretion:
> Renal impairment
> Hypertension
> Hypothyroidism
> Drugs e.g. alcohol, low dose aspirin, diuretics, cyclosporin
> Exercise, starvation, dehydration
> Lead poisoning
What is Lesch syndrome caused by?
Deficiency of the enzyme hypoxanthine-guanine phosphoribosyl transferase (HPRT)
What is the role of hypoxanthine-guanine phosphoribosyl transferase (HPRT)?
HPRT normally plays a key role in the recycling of the purine bases, hypoxanthine and guanine, into the purine nucleotide pools
In the absence of HPRT, these purine bases cannot be salvaged; instead, they are degraded and excreted as uric acid
The synthetic rate for purines is accelerated, presumably to compensate for purines lost by the failure of the salvage process.
How is Lesch Nyan syndrome inherited?
X-linked recessive
How does someone present with Lesch Nyan syndrome?
> Intellectual disability
> Aggressive and impulsive behaviour
> Self mutilation
> Gout
> Renal disease
Which population group is at highest risk of gout?
Older men
Why are men at higher risk for gout than women?
Men have higher urate levels than women and an increased prevalence of gout at all ages, though less pronounced in older age.
Oestrogen has a uricosuric effect, making gout very rare in younger women. However, after the menopause, urate levels rise and gout becomes increasingly prevalent.
When are woman at a higher risk of having gout and why?
Post menopause as Oestrogen has a uricosuric effect, this allows rate levels to rise and gout becomes increasingly prevalent
Why is increased age related with increased gout prevalence?
> An increase in sUA levels (mainly due to reduced renal function);
> Increased use of diuretics and other drugs that raise sUA;
> Age-related changes in connective tissues, which may encourage crystal formation;
> An increased prevalence of OA.
