Crystl arthropathies

Question 1

Site of absorption of urate

Answer 1

PCT -99% absorbed

URAT1, OAT4 -PCT anion transporters

Question 2

Urate and cardiovascular disease

Answer 2

Increased serum urate is associated with metabolic syndrome
HTN, hyperlipidemia,obesity, IGT
Mortality - CAD, HF,AF

Question 3

Interaction bet urate crystals and inflammatory system

Answer 3

Involves TLR,FC receptors,integrins
Phagocytosis by monocytes/macrophages
NLRP3 inflammasome assembly
Production of IL1beta>TNF,IL6, neurtrophil
Macrophage/osteoclast activation in bone lesions(tophi)

Question 4

Characteristic of gout crystal

Answer 4

Strongly negatively bifringent needle shaped crystals
Betamethasone crystals mimic urate crystals
Gout crystals can be found in asymptomatic joints

Question 5

USG imaging in gout

Answer 5

Tophus

Double contour sign -specificity 99%, sen -44%

Question 6

CT in gout

Answer 6

High accuracy for well established/tophaceous gout

More useful in knee and foot

Question 7

Biologic therapy of gout

Answer 7

Agents which inhibit IL-1beta suppress gouty inflammation

Anakinra, rilonacept, canakinumab

Question 8

Indications for urate lowering therapy

Answer 8

Recurrent flares, tophi,urate arthropathy, renal stones
serum urate >0.48
Renal impairment,HTN,IHD, heart failure

Question 9

Serum urate target

Answer 9

Low urate load - <0.36mmol/l

High urate load- <0.30

Question 10

Risk factors for allopurinol hypersensitivity

Answer 10

CAN BE VERY SEVERE
Renal insufficiency (CKD-3 or worse)
Thiazide use
Older age
Initial higher doses
HLA-B*58:01 (Chinese, Thai,Korean)

Higher maintainance dose not associated with hypersensitivity
Most common allergic reaction is rash

Question 11

Allopurinol dose in CKD

Answer 11

Start low dose -1.5mg per unit of GFR

Progressively increase dose till maximal effect

Question 12

MOA of febuxostat

Answer 12

DOC in allopurinol allergic/intolerant patients.Slightly superior to allopurinol
Xanthine oxidase inhibitor (non purine)
Rapid oral absorption
Hepatic metabolism. No dose modification in renal impair

Question 13

CV safety -allopurinol vs febuxostat

Answer 13

No difference in CV mortality but increased all cause mortality with febuxostat in studies

Question 14

MOA Probenecid

Answer 14

Inhibits URAT1, increases renal urate clearance
Requires eGFR >30-40
Good hydration needed, causes urinary alkalinisation
Add on to allopurinol/febuxostat

Question 15

MOA Benzbromarone

Answer 15

Most potent uricosuric
Inhibits URAT1
Requires GFR>20ml/min
Used in allopurinol failure
Close monitoring of LFT

Question 16

MOA Pegloticase

Answer 16

Pegloticase is a recombinant porcine-like uricase. Metabolises uric acid to allantoin.
S/E : Gout flares, infusion reactions, anti-pegloticase ab

Question 17

CPPD risk factors

Answer 17

Age, hemochromatosis,hyperparathyroidism,hypomagnesema

hypophosphatasia -low ALP

Question 18

CPPD presentation

Answer 18

Asymptomatic, non inflammatory arthritis,c/c inflammatory CPPD arthritis
Diagnosis- Xray shows chondrocalcinosis
Rod or rhomboid crystals
Can use Mtx

Question 19

Dangerous combination of drugs for gout

Answer 19

Febuxostat and azathioprine

Question 20

Dialysis amyloidosis

Answer 20

Beta2microglobulin amyloidosis
Affects patients undergoing long tem HD/PD
B2microglobulin invades synovial membranes and osteoarticular sites
Visceral manifestations rare

Question 21

Xray feature of pseudogout

Answer 21

Chondrocalcinosis

Question 22

IL involved in initiation of gout

Answer 22

IL- 1 beta