Psoriatic arthritis: Clinical sciences

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Introduction0:00–0:36

Psoriatic arthritis, or PsA for short, is a type of autoimmune arthritis that’s associated with a chronic inflammatory skin disorder known as psoriasis.
In psoriatic arthritis, inflammation leads to joint erosion and destruction, causing joint pain, swelling, and stiffness.
The assessment of patients with psoriatic arthritis involves Classification criteria for Psoriatic Arthritis, or CASPAR, which is a validated clinical tool used for diagnosis.
Okay, let’s look at a patient presenting with a chief concern suggesting psoriatic arthritis. The first step is to perform a focused history and physical examination.

Focused H&P, labs, and X-rays0:36–3:21

You should also order labs including rheumatoid factor, or RF, antinuclear antibodies, or ANA, C-reactive protein, or CRP, and erythrocyte sedimentation rate, or ESR for short.
Additionally, you should obtain X-rays of any affected joints. Your patient will typically report joint pain, stiffness, and swelling most commonly in the fingers and toes.
Psoriatic arthritis often targets the small joints of fingers and toes, but it can affect any joint. So don’t forget to ask about pain, stiffness, and swelling in larger peripheral joints like knees and elbows, and even in axial joints like spinal intervertebral and sacroiliac joints.
They may also have a personal or family history of psoriatic skin lesions. These present with dry, thick, and silvery-white scales, as well as a positive Auspitz's sign, which is the appearance of punctate bleeding spots when psoriasis scales are scraped off.Moving on, physical exam findings typically reveal joint tenderness and effusion, as well as dactylitis, sometimes described as sausage fingers.
You might also notice scaly erythematous plaques on the scalp, extensor surfaces of the limbs, and perineum. Other findings may include pitting of the nails.
Lab results will reveal a negative rheumatoid factor and ANA, and may show elevated CRP and ESR. Additionally, you will see positive HLA-B27 in around 10% of your patients!
Now, here’s a clinical pearl! The laboratory workup for autoimmune or inflammatory arthritis can be quite extensive.
You may need additional labs, such as c-ANCA and p-ANCA, anti-cyclic citrullinated peptide, and uric acid. Additionally, you might need to check Lyme disease serologies, complement levels, and joint fluid analysis.These tests can help you rule out other rheumatologic disorders, since they are typically negative in psoriatic arthritis!
For the X-ray findings, you might notice joint space narrowing, or joint margin ossification, also known as juxta-articular new bone formation.
In severe cases, there might be arthritis mutilans, which appears on X-rays as a pencil-in-cup deformity. At this point, you should suspect psoriatic arthritis!
Okay, once you suspect psoriatic arthritis, your next step is to assess the patient for the CASPAR criteria, which is a validated clinical tool commonly used to assess psoriatic arthritis.

CASPAR criteria3:21–4:25

To fulfill the CASPAR criteria, a patient must score 3 or more points based on the following 5 clinical findings. First, there should be evidence of psoriasis, such as current psoriatic skin changes, or personal history or family history of psoriasis.
The second one is current psoriatic nail changes like onycholysis, while the third is negative lab testing for rheumatoid factor.
Fourth is current or past history of dactylitis, and fifth is radiographic evidence of juxta-articular new bone formation.If your patient does not meet the CASPAR criteria, you should consider an alternative diagnosis.
On the other hand, if the patient does meet the criteria, you can diagnose psoriatic arthritis!Once you diagnose psoriatic arthritis, assess the disease severity.

Disease severity4:25–4:57

Factors to consider in the disease severity assessment include the number of joints affected, the severity of arthritis, enthesitis, and dactylitis, the degree of elevation in inflammatory markers, the degree to which the disease affects the patient’s ability to function, and how rapidly the disease is progressing.
Use your best clinical judgment to categorize psoriatic arthritis as mild, moderate, or severe, in order to guide treatment.
Okay, let’s start with mild disease activity. In this case, management involves NSAIDs for joint pain.

Mild 4:57–5:15

You may also add topical agents, like a corticosteroid, vitamin D analog, or calcineurin inhibitor to help control psoriatic skin plaques.Next we have moderate disease activity.

Moderate5:15–6:09

In this case, offer disease modifying anti-rheumatic drugs, or DMARDs, like methotrexate. In patients who have persistent joint inflammation despite 3 months of treatment with methotrexate, consider using another DMARD, like leflunomide.
In addition to DMARDs, you may also add a topical agent to help control psoriatic skin plaques.Here’s a high-yield fact to keep in mind!
Methotrexate works by inhibiting dihydrofolate reductase, an enzyme that is essential for folate metabolism. This can potentially cause your patient to have folate deficiency.
So, patients on methotrexate should also take a folic acid supplement. You should also be on the lookout for common adverse effects, such as gastrointestinal upset, hepatotoxicity, and in rare cases, myelosuppression!
Finally, let’s look at patients with severe disease activity. Management requires biologic medications, sometimes referred to as just biologics.

Severe6:09–7:36

Examples include tumor necrosis factor inhibitors, like etanercept or infliximab, and interleukin inhibitors, such as ixekizumab.
While these agents are likely to suppress both joint and skin manifestations of psoriatic arthritis, it's best to still offer a topical agent to help control psoriatic skin plaques.Here’s a high yield fact!
Biologics inhibit cytokine activity, effectively reducing the chronic inflammation linked to autoimmune conditions like psoriatic arthritis.
However, this can also suppress the immune system, increasing infection risk. So, before treatment, screen for latent Tuberculosis via a PPD skin test and make sure your patient’s vaccinations are up to date!
And here’s one last clinical pearl! Psoriatic arthritis is a chronic, progressive disease, so you should always reassess your patient’s symptoms to ensure adequate control.
For example, you may need to change treatment, like switching from a DMARD to a biologic depending on disease progression.
In addition, patients with psoriatic arthritis have a higher risk of developing atherosclerotic disease, so be sure to do an assessment of atherosclerotic risk factors; like diabetes, hypertension, and dyslipidemia.
Alright, as a quick recap... Psoriatic arthritis is an inflammatory autoimmune arthritis associated with psoriasis.

Review7:36–8:43

If you suspect psoriatic arthritis, use the CASPAR criteria to confirm the diagnosis. Once you diagnose psoriatic arthritis, assess the disease severity.
Factors to consider in the disease severity assessment include the number of joints affected, the severity of arthritis, enthesitis, and dactylitis, the degree of elevation in inflammatory markers, the degree to which the disease affects the patient’s ability to function, and how rapidly the disease is progressing.
Use your best clinical judgment to categorize psoriatic arthritis as mild, moderate, or severe, in order to guide treatment.Patients with mild disease activity can be treated with NSAIDs, while those with moderate disease activity are treated with DMARDs.
On the other hand, the management of patients with severe disease includes biologics. Finally, regardless of disease severity, all patients may need topical agents to help control psoriatic