Crystal disposition diseases

Question 1

What is a crystal disposition disease?

What are some examples of these common diseases

Answer 1

A disease characterised by deposition of mineralised material within joints and peri-articular tissue

Monosodium urate- gout
Calcium pyrophosphate dihydrate (CPPD)-pseudogout
Basic calcium phosphate hydrroxy-apatite, calcium periarthitis/tendonitis

Question 2

How is uric acid produced?

Answer 2

Through degradation of purine. The remainder is through diet. Of the uric acid produced daily 70% is cleared by the kidneys and the remainder filters into the biliary tract. People with gout have reduced renal clearance

Question 3

What factors lead to an overproduction of uric acid?

Answer 3

Malignancy e.g. tumour lysis syndrome
Severe exfoliatove psoriasis
Drugs e.g. ethanol, cytotoxic drugs
Inborn errors of metabolism
HGPRT deficiency

Question 4

How does alcohol increase puric acid production?

Answer 4

Some are rich in purines, metabolism of ethanol to acetyl CoA leads to adenine nucleotide degradation resulting in increased formation of adenosine monophosphate precursor of uric acid

Alcohol also raises lactic acid levels which inhibits uric acid excretion.

Question 5

What factors cause under excretion of uric acid

Answer 5

Renal impairment
Hypertension
Hypothyroidism
Drugs e.g. alcoholm low dose aspirin, diutetics
Exerccise, starvation, dehydration
Lead poisoning

Question 6

What is Lesch nyan syndrome?

Answer 6

HGPRT deficiency
X- linked recissive intellectual disability, aggresive and impulsive behaviour
Self mutilation
gout
renal disease

Question 7

Why is the HGPRT enzyme so important?

Answer 7

Normally plays a key role in the recycling of the purine bases, hypoxanthine and guanine into the purine nucleotide pools. In the abscence of this disease they cannot be salvaged leading to an overproduction of uric acid

Question 8

How do you treat an acute flare up of gout

Answer 8

NSAIDS
Colchine
Steroids (I/A, I/M, oral)

Question 9

What are the principles for treating hyperuricaemia associated with gout?

Answer 9

1st attack not treated unless singular attack of polyarrtiucar gout, urate calcufi, renal insfficiency
Treat 2nd attack if within 1 year
Prophylactically prior to treating malignancy
Do not treat asymptomatic hyperuricaemia

Question 10

How do you lower uric acid?

Answer 10

Xanthine oxidase ihibitor e.g. allopurinol
Febuxostat
Uricosuric agents e.g. suplphinpyrazone, probenecid, benzbromarone
Canakinumab

Question 11

What are the principles for lowering uric acid?

Answer 11

Wait until the attack has settled before reducing urate
Use prophylactic NSAIDS or low dose colchicine/steroids until urate level is normal
adjust allopurinol dose according to renal function
adjusting lifestyle factors can also be important

Question 12

What is pseudogout

Answer 12

The knee is to pseudogout as the toe is to gout. occurs in elderly females, with eratic flares
can have idiopahtic familial or metabolic causes
Can be triggered by trauma, intercurent or illness

Question 13

How do you manage pseudogout

Answer 13

NSAIDS
I/A steroids

There are no prophylactic therapies

Question 14

What is polymagia rheumatica?

Answer 14

Sudden onset of shoulder (+pelvic girdle stiffness). 
Typically 70+
ESR usually >45
Anaemia
Malaise, weight loss, fever, depression
Arthralgia, synovitis occasionally

Question 15

How is a diangosis confirmed in polymagia rheumatica?

What condition is associated with PMR

Answer 15

Compatible history, no specific diagnostic test
Age>50
ESR>50
Dramatic steroid response

Giant cell arthritis

Question 16

What are some differentials for polymagia rheumatica

Answer 16

Myalgic inflammatory joint disease
Underlying malignancy
Inflammatory muscle disease
Hypo/hyperthyroidism
Bilateral shoulder capsulitis
Fibromyalgia

Question 17

What is the treatment for polymagia rheumatica?

Answer 17

Prednisolone 15mg oer day initially
18-24 month course
Bone prophylaxis