Psoriatic arthritis is an autoimmune disease that can lead to swelling, pain, and stiffness in the joints. This painful condition can affect any joint in the body, but most often it impacts the fingers and toes, as well as the ankles, knees, wrists, and lower back or spine. Because many symptoms of psoriatic arthritis aren't so easy to spot (joint pain, fatigue), it is often referred to as an "invisible" disease. However, other psoriatic arthritis symptoms are more identifiable.

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The symptoms of psoriatic arthritis can differ greatly from person to person. The number of joints affected by the disease can vary, and at times a patient may only exhibit symptoms on one or two of their joints, while at other times the disease can impact several joints at once. Often—although not always—psoriatic arthritis is asymmetrical, meaning a joint on one side of the body is affected (your knee, for example), while the mirror-image joint feels normal.

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Copyright 2017 American College of Rheumatology

Joints that are close to each other on the body can also be impacted very differently. "You can have severely involved joints [with] nearby joints showing almost complete preservation," says Ted Mikuls, MD, professor of internal medicine in the division of rheumatology at the University of Nebraska Medical Center in Omaha. "It can be very spotty."

Psoriatic arthritis symptoms in the fingers can be very distinctive. One possible symptom is the last knuckles of the finger (near the nails) swelling and becoming inflamed, while other joints in the finger remain unaffected. Other telltale signs of psoriatic arthritis can be seen on the nails themselves: pitting, grooving, or other textural changes on the nail bed; changes in color; or thickening of the nails. Sometimes the nails can separate entirely on the nail bed. Some of these changes may cause patients to think that they have a fungal infection.

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Copyright 2017 American College of Rheumatology

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Copyright 2017 American College of Rheumatology

Another possible symptom of psoriatic arthritis is dactylitis, when the entire finger or toe swells up to look like a sausage. "That is really characteristic for psoriatic arthritis," says Dr. Mikuls.

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Copyright 2017 American College of Rheumatology

Psoriatic arthritis can also result in deformities in the joints. In fact, deformities may happen even before you experience some of the other hallmark symptoms of psoriatic arthritis like joint pain and stiffness. In the feet, deformities can occur in the form of clawed toes (they bend up or down) or ankles that roll inward. Some people also develop calluses or corns on the bottoms of their feet.

Psoriatic arthritis can also affect parts of your body in addition to the joints. Redness, irritation, and pain in the eyes, including conjunctivitis, can also be a sign of psoriatic arthritis, as can fatigue.