PSA is commonly used in medicine to refer to Prostate Specific Antigen which is a protein produced by the prostate gland that is measured as a marker of prostate enlargement, prostate cancer and prostatitis.
However in a paper published by Dr Mercola who is a dermatologist and rheumatologists as well as an assistant professor at Harvard Medical School, PSA has become a mnemonic for:
P Pain in joints which are often swollen
S Stiffness for more than 30 minutes after rest AND/OR Swollen, sausage-shaped fingers or toes
A Axial spine involvement characterized by symptoms like a stiff back
This PSA represents symptoms of inflammatory arthritis and psoriatic arthritis.
It is an important mnemonic for dermatologists because many skin conditions also have rheumatological symptoms. Common examples of such conditions include psoriasis, dermatomyositis and lupus erythematosus.
This mnemonic will serve as a reminder for dermatologists seeing patients who mention any of the PSA symptoms. It will remind them to inquire about other systemic symptoms of these dermato-rheumatological diseases. It these are present, it will lead to a more extensive physical examination, ordering of serologic and radiologic tests and referral to a rheumatologist for co-management.
PsA, with a small s, is also used in dermatology to stand for Psoriatic arthritis. In addition to the above PSA symptoms, patients with PsA can also present with:
1. Nail pitting which can be associated with thickening and discoloration.
2. Enthesitis or pain in areas where tendons attach to bones like the heel (Achilles tendinitis), sole (plantar fasciitis), knees and hips.
Another important point to remember when examining a patient with PsA and PSA is that there are 5 types of PsA:
1. Symmetric psoriatic arthritis which affects similar joints on both sides of the body is often confused with rheumatoid arthritis.
2. Asymmetric psoriatic arthritis which affects both small and large joints like the hip and knee and can be confused with osteoarthritis.
3. Distal interphalangeal predominant (DIP) which affects the small joints of the fingers and toes and can be confused with osteoarthritis.
4. Spondylitis which affects the vertebrae and sacroiliac region and can be confused with osteoarthritis.
5. Arthritis mutilans which is the severe and destrictive form that usually destroys the small joints of the fingers and toes.