Gout, Pseudogout, and Joint Pain

 

The most common joint affected by gout is the first metatarsophalangeal joint. The most common joint affected by pseudogout is the knee joint. Gout and pseudogout both show a sudden onset of pain, redness, and swelling typically affecting a single joint in 80% of the cases. 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. Gout crystals are needle shaped and negatively bifringent. When placed under polarized light, they will be yellow. 90% of patients suffering from gout are men between the ages of 40-60 years old. Uric acid buildup in the body occurs by two main mechanisms: 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. Gout symptoms and signs 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 “punch-out” lesions. The tophi occurs due to deposition of uric acid crystals. The tophus aspirate may look like tooth paste. 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 amounts of meat or seafood, or trauma/surgery. Other risk factors for gout are obesity, hypertension, and diuretics. Red meats, seafood, liquor, beer, all increase the risk of gout. Vegetables, wine, dairy products, and total proteins do not increase the risk of gout. Aspiration and analysis of the joint fluid is the best method for diagnosis. Elevate uric acid is not diagnostic. 80% of people with elevated uric acid will not get a gouty attack. There are blood tests such as white blood cell count, C-reactive protein, sedimentation rate, and uric acid level that are helpful in supporting the diagnosis if elevated, but if these levels are normal, it cannot definitively rule out gout or pseudogout. Every time you aspirate a joint and you get synovial fluid, you need to analyze it for cell count differential, find out if you have crystals or not and send the fluid for culture and sensitivity if you suspect infection. It might be difficult to differentiate an acute gouty attach from acute septic arthritis. Patients with an acute gouty arthritis may not have an elevated serum uric acid level. A patient with acute gouty arthritis may present with symptoms and a clinical picture that is similar to septic arthritis. Aspirate the joint fluid, and the joint fluid will look like pus, but it could be gout. You will take the fluid and examine it under the microscope (you will find needle shaped, intracellular crystals, and you will think that it is gout). The cell count of the aspirate may be high (may be 50,000-60,000) and the neutrophils may also be high (may be 80%). The incidence of gout and associated septic arthritis of a joint is low (about 1.5%). The incidence of septic arthritis will increase to 11% or more if the cell count is more than 50,000. We aspirate the joint (aspirate will look cloudy, like pus). We look for crystals and if there is crystals, then it is gout, but the presence of uric acid crystals does not exclude septic arthritis. We look at the cell count (will be high, 50,000 or more). The neutrophil count may be 80% or more (we think there is an infection in addition to gout or maybe gout alone). We need to culture the fluid. After we aspirate the fluid and send the fluid for culture, then we give the patient empiric intravenous antibiotics pending the culture result. Remember that gout and septic arthritis can occur together, but the incidence is low. The incidence will increase significantly if the cell count is more than 50,000. Pseudogout or chondrocalcinosis is the deposition of calcium pyrophosphate dihydrate 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. Pseudogout most often affects the knee, occurs more in older patients, and is a calcification of fibrocartilage (chondrocalcinosis). Pseudogout crystals are rhomboid shaped and positively birefringent. Crystals will be blue when placed under polarized light. Associated conditions include hyperparathyroidism, rheumatoid arthritis, and gout. Aspirate to see if it is pseudogout or infection, because you do not want to inject the knee with steroids when there is an infection. You need to look for the rhomboid crystals of pseudogout. X-rays in pseudogout will show thin calcification in the articular cartilage or menisci. Calcifications of the synovium, tendon, and ligaments can also occur. Acute gout can be treated with indomethacin or colchicine if the patient cannot tolerate NSAIDs. Colchicine inhibits the inflammatory mediators and is indicated if the patient cannot tolerate indomethacin. Chronic gout can be treated with allopurinol to prevent buildup of uric acid. Allopurinol is a xanthine oxidase inhibitor. Pseudogout is treated with NSAIDs and intraarticular injections.