3. Gout Flashcards
Epidemiology of Gout
Starts in puberty – serum levels rise from 3.5 in kids to 5.0 in adult males
Seen mostly in 50 yr old men – most common cause of inflammatory arthritis in men over 30 yrs
o only about 5% of gout is in women and 90% of those cases are postmenopausal
estrogen promotes renal excretion of uric acid
o 1:1 M:F after menopause
Hyperuricemia is 2 standard deviations past the mean
7.0 in men, 6.0 in women
o Present in 5% of all people (25% of those people develop gout)
Not everyone who is hyperuricemic develops gout! (only 1⁄4)
Predisposing Factors:
Obesity
o Genetics
o High protein intake
o Stress, Trauma
o Infection
o Alcohol, Drugs
Most people w/ gout are underexcretors
Unusual Presentations of Gout
Unusual Presentations of Gout
Early-onset Gout – between 3-6% present before 25 yrs
o Increased risk up to 80% w/ family history
o Leukemia can cause early onset
Transplant Gout – seen in 75% of heart transplants while on cyclosporine and 50% of liver/kidney
Normouricemic Gout – gouty attacks w/o elevated uric acid levels (trippyyyy)
Cause of Gout: (remember, normally – purine degradation leads to uric acid)
In gout, there are 2 problems that can lead to hyperuricemia:
o Uric Acid Overproduction - >800mg in 24hrs
Primary Overproduction – most idiopathic, but can be caused by:
HGPRT/Lesch-Nyhan
PRPP Synthetase Superactivity
Secondary Overproduction – can be caused by:
Excessive dietary intake
Things that increase nucleic acid turnover
o Psoriasis
o Myelo- and Lymphoproliferative problems o Hemolytic disease
Things that accelerate ATP degradation: o Alcohol abuse
o Severe muscle exertion
o Glycogen storage disease
Uric Acid Overproduction accounts for 10% of gout cases
Cause of Gout
o Uric Acid Undersecretion – renal deficits account for 90% of gout cases
Primary Undersecretion – idiopathic
Secondary Overproduction – due to decreased renal function
Inhibition of tubular urate secretion
Enhanced tubular reabsorption Dehydration of diuretics
Insulin resistance
Gout – 5 stages:
Asymptomatic Hyperuricemia – high uric acid levels w/o any attacks
Acute (Intermittent) Gouty Attack – local calor, swelling, and erythema w/ intense pain
o Erythema can extend beyond the joint and resemble sepsis
o Pain crescendos up to a peak over 8-12 hrs
Pain can last for hours (mild) or weeks (severe)
o Monoarticular – 1st MPJ is seen in 50% of initial attacks, and 90% over time
o Systemically – fever, chills, and malaise
o Between attacks the patient is asymptomatic (intercritical)
Intercritical Gout – asymptomatic period in joints previously involved in gouty attack
o No clinical symptoms, but MSU crystals are found in synovial fluid
Also higher synovial fluid inflammatory cell count (shows subclinical inflammation)
o in early disease intercritical/asymptomatic period can last years, but shortens w/ disease progress
Chronic Tophaceous Gout – unlike acute, there is pain during the intercritical periods
o Develops after >10 yrs of acute intermittent gout
o Joints are persistently painful and swollen; but the intensity is less than an acute attack
Renal Disease/Gouty Nephropathy
Clinical Labs and Diagnosis
Presumptive Diagnosis – a diagnostic triad that is probably gout:
o acute monarticular arthritis
o increased serum uric acid levels
o symptomatic improvement w/ colchicine
Clinical Labs and Diagnosis
Definitive Diagnosis – only way to know for sure it’s gout
o Analysis of synovial fluid or tophaceous material that demonstrates MSU crystals
Done w/ Compensated Polarized Microscopy
Negative birefringence, bright yellow needle/rod-shaped crystals
Crystals are usually intracellular during an attack – ingested by PMN’s
o Synovial Fluid falls under Group II Inflammatory
Clinical Labs and Diagnosis
Elevated serum levels
Elevated serum levels – not the best diagnostic value
o Actually can be normal during an attack (frequent occurrence) o Majority of hyperuricemic pts never develop gout
Common Pedal Sites of Gouty Arthritis – can attack any site in the foot though!
o 1st MPJ – in 90% of gout cases
o 1st IPJ
o Lisfranc’s Joint
o Ankle joint
Gout
Most common pedal sites
1st mpj most common-90%
Lisfranc’s joint
IP joint hallux
Ankle joint
Radiographic Features of Gout
o Acute Gout:
o Soft-Tissue Swelling – non-specific periarticular inflammation
Usually monoarticular
o No crystals, erosions, joint space widening, or osteoporosis yet
Takes 6-8yrs post onset to detect erosive changes on radiographs!
o No underlying OA
Radiographic Features of Gout
o Intercritcal Gout –
period shortens w/o treatment and attacks become frequent, polyarticular, & longer
o Periarticular Calcifications
o Erosions - centered over the capsulo-synovial attachment zone o Early Interarticular Damage
o Underlying OA changes (marginal joint space narrowing)
o Chronic Tophaceous Gout –
most commonly asymmetric polyarthritis
Can be bilateral and symmetrical though
Chronic gout
Tophae
– eccentric periarticular soft tissue masses w/ underlying boney erosions
Can clinically mimic exostoses
Their subchondral bone appears cystic
Central joint “eruption” (center of joint is bright) Tendinous masses w/ underlying erosions
Seen especially in Achilles tendon
Occasionally, tophae calcify
*remember RA nodules don’t have bony changes under them
o Large Intra- & Extra-articular Erosions
Erosions tend to involve joint margins before extending centrally
“Punch out” w/ a sclerotic margin
Overhanging Margins
Depends on timeline:
Early – marginal and small (still have 50% capsular attachment)
Progressive Gout – usually >5.0mm
o w/ both intra- and extra-articular involvement
o concentric distribution across joint
Erosions that pop up right in the center are seen in gout (not seen in RA)
Joint Space Preservation – throughout disease
Even though erosions cross the joint, the joint space is spared
In very late in disease, is the joint space lost
o Normodensity Subchondral bone – even though there are erosions, bone isn’t brighter or darker
Gout
Detecting erosive changes
It takes 6-8 yrs post onset to detect erosive changes on radio
Wo treatment
Intercritical period shortens, attacks beecome more frequent, polyarticular, and of longer duration
Other Radiographic Features associated w/ Gout
o Chronic Midfoot/Arch Pain due to erosions in midfoot and rearfoot bones o End-stage Gout can resemble malignancy!
o Gout doesn’t produce osteopenia or
osteosclerotic changes; it involves more extra-
articular changes
o Medullary Infarct – associated w/ chronic gout
Gout – MSU crystal deposition in tissues from supersaturation of uric acid in extracellular fluid
Gouty Arthritis – recurrent arthritic attacks of gout
Tophi – accumulation of articular, osseous, soft tissue, and cartilaginous crystalline deposits
Stones – uric acid caliculi in the urinary tract
Gouty Nephropathy – interstitial nephropathy w/ functional impairment of kidney
