Diagnosing psoriatic arthritis (PsA) can be tricky, primarily because it shares similar symptoms with other diseases such as osteoarthritis, rheumatoid arthritis, and gout. Because of this, misdiagnosis can often be a problem. Early diagnosis, however, is important because long-term joint damage can be warded off better in the first few months after symptoms arise.
PsA can develop over a long period of time, or it can appear quite suddenly. PsA may strike at any age, but most commonly begins between the ages of 30 and 50, impacting men and women equally. While children can also get psoriatic arthritis, it is rather rare.
Primary care physicians and dermatologists can diagnose PsA, but a rheumatologist, who specializes in arthritis, may be able to better spot the telltale signs of the disease.
There are no definitive tests for diagnosing PsA. Doctors diagnose the disease primarily based on a patient’s clinical presentation and process of elimination (for example, the presence of rheumatoid factor in the blood can differentiate rheumatoid arthritis from PsA.) A complete medical history and physical examination, as well as blood tests, X-rays, and MRI scans of joints that have symptoms, can be used to diagnose PsA.
In the early stages of the disease, standard X-rays usually don’t reveal signs of PsA and may not aid in diagnosis. In later stages, however, they may show characteristic changes that distinguish PsA from other rheumatic diseases. One of these is the “pencil-in-cup” phenomenon, in which the end of a bone gets whittled down to a sharp point where it enters a joint. Changes in the peripheral joints and spine, which also occur in later stages of disease, can also support a PsA diagnosis.
A diagnosis of psoriatic arthritis can be made more easily if there is active psoriasis, as well as swollen fingers or toes, when the patient is seen. If nail involvement is also apparent, a firm diagnosis of PsA can commonly be made.
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