Why is PsA called a disease of exclusion at age 30?

Question

Hi doctor,

I am 30 years old, and my rheumatologist said that she thought that I might be suffering from psoriatic arthritis. I also learned from him/her that it is a disease of exclusion, but I did not get the meaning behind this term.

Is it true that there is no diagnostic tool through which you could confirm psoriatic arthritis? Why does it take such a long time then to make a diagnosis?

Any help in this regard will be appreciated.

Thank you very much.

Answer 1

Hi,

Welcome to icliniq.com.

I appreciate your concern.

Wishing you all the best.

There is no one test for the confirmation of psoriatic arthritis. It is easy to diagnose psoriatic arthritis when classic lesions of skin psoriasis are present. However, when skin manifestations are not present, diagnosing psoriatic arthritis becomes difficult because psoriatic arthritis can mimic other forms of inflammatory arthritis, such as rheumatoid arthritis, lupus arthritis, or even calcium pyrophosphate disease.

When diagnosing psoriatic arthritis is difficult, it is made based on clinical evaluation of symptoms, physical examination findings, imaging results, and elimination of other causes of arthritis.

Some signs making psoriatic arthritis probable include:

Having relatives with psoriasis, since psoriasis is a condition which has a genetic factor, and there may be cases when joint problems occur first, and skin problems occur after.
Presence of enthesitis, which means inflammation at the site of attachment of a tendon or ligament to bone. Enthesitis often involves tendons such as the Achilles tendon or plantar fascia.
Spine or sacroiliac joint involvement, which might manifest in the form of lower back pain that is worse when resting, with signs of inflammation on magnetic resonance imaging (MRI scans).
Involvement of the distal joints of the fingers (joints nearest to the nails).
Nail changes related to psoriasis.

These symptoms can help distinguish psoriatic arthritis from other inflammatory joint conditions in cases when there are no typical skin lesions or other clear-cut signs of psoriasis.

When it comes to treatment, there is a number of medications one should avoid if they suspect they have psoriatic arthritis due to the potential exacerbation of the skin manifestation of the condition by those drugs, including corticosteroids and hydroxychloroquine.

The use of methotrexate can be an effective choice for the initial therapy. If this drug proves insufficient, biologics might be used.

Prior to commencing any treatment, the following tests should be considered:

Complete blood count (CBC).
ESR & CRP (inflammatory markers).
ALT & AST (liver function tests).
Serum creatinine (renal function test).
Anti-hepatitis C antibody (HCV Ab).
Hepatitis B surface antigen (HBsAg).

Concerning treatment, there is a general agreement that Methotrexate 25 mg weekly can be regarded as one of the first-line options, together with Folic acid supplementation in the dose of 5 mg once weekly.

Follow-up is usually carried out three months after the initiation of Methotrexate, for evaluation and further adjustments, if necessary.

It should also be mentioned that apart from medications, additional treatment, including sufficient rest during periods of exacerbation and physical therapy, involving proper exercises, is recommended.

I hope that I have answered your questions.

Thank you.