Doctor... How Do You Diagnose Psoriatic Arthritis?

atic arthritis (PSa) is one of the most common formsTo make things more confusing, a patient may have
of inflammatory arthritis.concurrent psoriasis and rheumatoid arthritis, psoriasis
It is defined as a “unique inflammatory arthritisand osteoarthritis, or no known psoriasis, which can
associated with psoriasis.” Estimates of itsreally complicate the diagnosis of PsA. Sometimes,
prevalence in the general population vary from 0.3% topatients will have a family history of psoriasis or
1%.psoriatic arthritis.
Initially, PsA typically presents as an inflammatorySince it is a systemic form of arthritis, much like
arthritis affecting one or perhaps a few joints.rheumatoid arthritis, patients with psoriatic arthritis can
However, over time PsA may begin to involve manydevelop complications such as inflammatory eye
joints and becomes very severe in at least 20% ofdisease.
patients.The Classification criteria for Psoriatic Arthritis
So how does a patient know when they have(CASPAR) are diagnostic parameters that were
psoriatic arthritis?recently formulated by researchers to standardize the
Unfortunately, few solid diagnostic clinical criteria arediagnosis of PsA. The system may be used in the
present.future for clinical trials involving patients with PsA.
And… there are no clear cut research criteriaClassification criteria for Psoriatic Arthritis
for the diagnosis of PsA- even the experts have not(CASPAR) Criteria:
formulated widely accepted parameters. The diagnosisPresence of inflammatory joint disease (joint, spine or
has been based on the presence of inflammatoryenthesis [where the tendon inserts into bone]) with at
arthritis which may affect either peripheral joints suchleast 3 points from the following 5 categories:
as the fingers, wrists, elbows, shoulders, hips, knees,1. Evidence of current psoriasis, personal history of
ankles, or toes. Or the disease may affect thepsoriasis, or family history of psoriasis.
sacroiliac joints (joints that joint the spine to the pelvis)2. Typical psoriatic nail changes, including onycholysis
plus the presence of psoriasis and the absence of a[separation of the nail from the nailbed], pitting, and
positive rheumatoid factor in the blood.hyperkeratosis (thickening and discoloration) on
PsA does often cause a peculiar type of joint swellingexamination.
called “dactylitis.” This is often referred3. Negative test result for rheumatoid factor
to as a “sausage digit”4. Current dactylitis, defined as swelling of an entire digit
because…. well, because the affected swollen(finger or toe), or history of dactylitis recorded by a
finger or toe looks like a sausage!rheumatologist.
Experienced clinicians can make the diagnosis usually5. X-ray evidence of juxta-articular (“next to
although this is not a diagnosis that can be madethe joint”) new bone formation appearing as
easily… particularly at the beginning.ill-defined ossification (“calcium deposits”)
The erythrocyte sedimentation rate (ESR ornear joint margins on plain x-rays of hand or foot.
“sed rate”) is elevated in 40% to 60%Once the diagnosis has been established, treatment
of patients. X-ray findings may be absent in earlycan be instituted. The topic of treatment for psoriatic
disease. Magnetic resonance imaging and diagnosticarthritis will be discussed in another article. Stay tuned!
ultrasound may be more useful in early disease.