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Pseudogout and Calcium Pyrophosphate Deposition Disease

Medication history is important because of things like thiazide, since it can cause hyperuricemia. Recent surgeries, hospitalizations or other illness are known to precipitate attacks of crystal disease, both gout and pseudogout. So thatís an important thing to elicit is itís somebody thatís presenting with an acute monoarticular arthritis.

When you evaluate this patient, certainly several things are very important. We always like to start with a physical examination. X-rays, obviously most importantly to rule out traumatic events, but also you can get clues of crystal disease. Synovial fluid to aspirate for culture then also to look for crystals in the fluid, and other laboratory studies.

Crystal identification: for the best identification of your crystals you really need a red-compensated polarized microscope. Like I asked yesterday, I donít think anybody here has one. The challenge is that some of your pathology departments donít even have them. I was in practice for six years in a 1,000 bed hospital and the entire hospital.

They only cost a couple of thousand dollars for a big institution, but their idea of a polarized microscope was using a couple of polarizing filters over the eyepiece and over the light source, which is fine if you canít afford anything else or itís not practical, but for a big institution is was kind of silly and it makes it a little more challenging because although you can tell crystals are present, you cannot tell birefringence unless you use a red-compensated polarized microscope. Weíll take a look in a second at monosodium urate crystals for gout. There are CPPD crystals. Occasionally you can see other crystals. Cholesterol crystals, steroid crystals can be somewhat confusing sometimes. When you get beyond those crystals, particularly things like hydroxyapatite crystals you actually need to use either very special stains or electron microscopy.

This is using the red-compensated polarized microscope. This is a monosodium urate crystal and what this does is, you have the axis of your compensator - if you remember your negatively birefringent Ö what negative birefringence is, is that when the crystal is parallel to the axis of the compensator, it is yellow. I always just remember that parallel has got two llís and so does yellow and they sort of look parallel. So for the negatively birefringent for gout, that would be parallel. If it is perpendicular it turns blue. Interestingly enough, when you are halfway in between there you canít see it at all. The ability to rotate the crystals sometimes is important. If you just so happen to have only a couple of crystals and they are oriented the wrong way.

This is a calcium pyrophosphate crystal. You can see itís more a rhomboid-shaped crystal. Itís not the same needle shape. This is what it looks like under a polarizing system, but we used the red compensation. You can note the direction of the birefringence. So the calcium pyrophosphate crystal is weakly positively birefringent whereas the monosodium urate crystal.

Pseudogout is one manifestation of calcium pyrophosphate deposition disease. CPPD can cause a number of different arthritic presentations. One of which is pseudogout. Itís called that because it looks sort of like gout, but in general though it is not as intense as gout. The knee is more commonly involved than the foot and itís often precipitated by surgery or trauma or heart attack or congestive heart failure, or something of that nature. Iíve seen it in the hospital after the elderly patients have had surgical procedures or an acute medical event. What happens is that they have these crystals in the lining of the joint and these crystals get shed into the joint space and the crystals are highly inflammatory. When you look for crystals in CPPD disease there is usually much fewer crystals present than when you see gout. Oftentimes if you get a gout fluid, there is no question when you look at that fluid. Thereís just hundreds and hundreds of crystals in there. Often with CPPD youíve got to look for four or five minutes and you are told not to call a synovial fluid negative for CPPD.

The laboratory testing is really only useful when you are looking for concomitant illnesses, hyperparathyroidism. There is nothing particularly that you are going to find in a patient with pseudogout itself. The synovial fluid tends to again have that inflammatory characteristic of slightly yellowish, slightly cloudy, poor viscosity, high white count and a predominance of polys. You again look for the rhomboid-shaped, weakly positively birefringent crystal. X-ray typically are normal. You may see soft tissue swelling. I showed you some pictures of the chondrocalcinosis - I think I have another one here - is the only real characteristic that you see on an x-ray. Does chondrocalcinosis mean pseudogout? No. I means that theyíve got calcium at the cartilage border but it may be that that calcium that is shedding into the joint. So there is an association with chondrocalcinosis and pseudogout.

Pseudogout treatment is a little different in that chronic management isnít Ö you are not trying to manage someone the same way, of lowering uric acid like you do in gout. Treatment acutely can be just to aspirate it. Often just taking the crystals out will get rid of the inflammatory process. Steroid injections are the way I would usually treat it if I could. Oral colchicine does work, less rapidly than with gout. NSAIDís often work just as well. Chronically we donít have the magic we have in gout and we end up getting stuck with long-term oral colchicine or non-steroidals.