The most common joint affected by gout is the 1st
metatarsophalangeal joint. The most common joint affected by pesudogout is the
knee joint (Figure 1). Gout and pseudogout are similar problems with different
causes.
Gout is caused by the buildup of uric acid and the deposit
of uric acid crystals inside a joint. The best test to diagnose gout is with a
joint fluid analysis. Elevated uric acid is not a good criteria. 90% of
patients suffering from gout are men between the ages of 40-60 years. Gout
crystals are needle shaped and negatively birefringent. When placed under
polarized light they will be yellow (Figure 2).
Uric acid builds up the body by two main mechanisms. These
two mechanisms are excessive urate production and diminished urate clearance.
Uric acid is produced from the breakdown of proteins inside the body and from
the proteins of food that is eaten.
Precipitating Factors:
The sudden attack of gout can be brought on by anything that
increases the level of uric acid in the blood such as dehydration, increased
consumption of alcohol, eating large amount of meat or seafood, and
trauma/surgery.
Diagnostic Testing:
Aspiration and analysis of the joint fluid is the best
method for diagnosis (Figure 3). There are blood tests such as white blood cell
count, C-reactive protein, erythrocyte sedimentation rate, and uric acid level
that are helpful in supporting the diagnosis if elevated, but if normal, it
cannot definitively rule out gout or pseudogout.
Pesudogout or chondrocalcinosis is the deposition of calcium
pyrophosphate dehydrate crystals in the hyaline cartilage or fibrocartilage
(CPPD). Pseudogout is a metabolic disease where calcium pyrophosphate dehydrate
crystals (CPPD) are formed within the joint space. It most often affects the
knee and occurs more in older patients. It is a calcification of fibrocartilage
(chondrocalcinosis). Pseudogout crystals are rhomboid shaped and positively
birefringent. Crystals will be blue when placed under polarized light (Figure
4). Associated conditions are hyperparathyroidism, rheumatoid arthritis and
gout.
Gout and pseudogout both show a sudden onset of pain,
redness and swelling typically affecting a single joint in 80% of the cases.
Gout symptoms include joint pain, swelling and arthritis. Patients with gout
have periarticular erosions along with the formation of uric acid soft tissue
masses in and around the joint which can be seen on x-ray. Soft tissue tophus
deposition with periarticular erosions called “punch-out” lesions (Figure 5).
X-rays in pseudogout will show this calcification in the
articular cartilage or menisci, with involvement of the patellofemoral joint
(Figure 6). Calcifications of the synovium, tendon, and ligaments can also be
seen.
Treatment of Gout and
Pseudogout:
Acute gout can be treated with indocine and colchicine (be
aware of peptic ulcer). In cases of chronic gout the patient will be treated
with allopurinol (xanthine oxidase inhibitor) and colchicine. Uricosuric drugs
such as Probenecid may increase uric acid excretion by the kidneys may be
helpful. Pseudogout is treated with NSAIDs and intra-articular injections.
