Leann Bassing, MD, Board Eligible Rheumatologist at Yankton Medical Clinic, P.C.
Most people don’t realize there is a specific kind of arthritis that can accompany psoriasis skin disease. That is, until commercials of professional golfer Phil Mikkelson endorsing a medication to treat his own diagnosis of Psoriatic Arthritis (PsA) started to appear on television. First of all, Psoriasis is a disease that is typically manifested as thickened red scaly plaques on the surfaces of elbows or knees, but also can occur on the scalp or trunk. My physical examination of new patients usually includes a close inspection of these areas, as well as a few areas where psoriasis likes to ‘hide,’ including the external auditory ear canal, umbilicus (belly button), nails, and superior gluteal cleft (top of the buttocks). If I can find any clues in these areas, it can affect the diagnosis in a significant way!
Psoriatic arthritis (PsA) is an inflammatory joint disease that not only can cause inflammation in joints, but also inflammation of tendons. Another important difference of Psoriatic arthritis from Rheumatoid arthritis, which is the most common type of inflammatory arthritis, is PsA’s ability to affect the joints of the low back, or specifically, the sacroiliac joints. These are two long joints where the tailbone meets the pelvis. Typically, patients who have inflammation in these joints, called Sacroiliitis, will experience significant low back stiffness that is most prominent in the mornings. This is because inflammation is more prevalent after being inactive throughout the night. When PsA was defined as a specific disease entity back in the early 1970’s, five subsets were identified based on clinical features. These include number of joints involved (polyarticular = 5 or more joints versus oligoarticular = 4 or fewer joints affected), pattern of joint involvement (distal interphalangeal = small knuckles at the ends of the fingers versus spondylitis = spine is affected), and possible deforming arthritis (mutilans) (1).
Estimates of how many people with psoriasis are also affected by PsA vary greatly depending on the study method. The frequency of PsA in patients with previously diagnosed psoriasis varies from 1% to 39%, with the wide range existing mainly due to differences in diagnostic criteria (1). Most people are between the ages of 30-55 years old at the time they are diagnosed, and men are as equally affected as women. While most patients have psoriasis before the arthritis shows up, interestingly up to 30% will have the inflammatory joint disease before any skin symptoms, half of those not developing skin disease for more than a year after the arthritis findings. You can imagine, this can make an accurate diagnosis a bit more difficult. A few unique features of PsA that can help with making the diagnosis include occasional findings of a diffusely swollen digit, or ‘sausage-shaped digit,’ called dactylitis (this is due to inflammation that runs along the length of a tendon lining the finger or toe), or inflammatory eye disease, especially anterior uveitis, in which the patient may experience a red painful eye and an ophthalmologist can actually identify inflammatory cells within the eye itself. X-rays of the hands, feet, or sacroiliac joints can also reveal some distinct bony features of PsA, unique from other forms of arthritis. There is no single blood test that can make the diagnosis, however.
Thankfully, we do have relatively good medications to treat PsA. These include non-steroidal anti-inflammatory drugs (NSAIDs), disease modifying anti-rheumatic drugs (DMARDs), or biologic medications (anti-TNF drugs such as the etanercept Phil Mikkelson tells us helps his PsA…disclaimer: these medications won’t necessarily improve your golf game!).
If you or someone you know has joint pain, especially joint swelling combined with psoriatic skin disease, make an appointment with a Rheumatologist. An accurate diagnosis and appropriate treatment may be closer than you think.
- Firestein, GS. Et al. Kelley’s Textbook of Rheumatology, 8th Ed. Saunders, 2009.
- Canti, F. et al. Psoriatic arthritis: a systematic review. International Journal of Rheumatic Disease (2010) 13: 300-317.