Psoriatic arthritis (PsA) is an inflammatory arthritis that occurs in up to 30% of psoriatics. It is typically considered a seronegative inflammatory arthritis, ie, without detectable rheumatoid factor. About 15% of patients develop PsA before skin psoriasis is present.
The etiology of the disease is multifactorial, with both genetic and environmental factors. PsA affects men and women equally and is predominantly seen in white individuals, similar to psoriasis.
Pain, stiffness in affected joints, with joint stiffness present for > 30 minutes in the morning (after waking) or after prolonged inactivity. Improves with activity (versus osteoarthritis / degenerative joint disease, which typically worsens with activity).
With axial involvement – Inflammatory back pain and stiffness that improve with activity; night symptoms can cause waking from sleep; decreased range of motion of the axial spine and neck over time.
Tender / painful; swelling at entheses (sites of tendon insertion into bone).
Tendonitis / tenosynovitis
Ocular inflammation may lead to scleral erythema, dry eye / foreign body sensation, or uveitis with potential visual disturbance and pain.
Hearing loss is increased in patients with PsA.
Tender, painful, swollen joints with possible erythema, effusion, and warmth noted in more actively inflamed joints.
Dactylitis – Inflammation and swelling of the entire digit including metacarpophalangeal (MCP) through proximal / distal interphalangeal (PIP/DIP) joints and intervening soft tissue, giving a "sausage digit" appearance.
Enthesitis – Inflammation at tendinous insertion into bone, with tenderness.
Note: Patients do not necessarily fit into any one pattern and may have features of several throughout the course of illness.
Patients with nail, scalp, and inverse (intertriginous) psoriatic skin disease have a higher risk of developing PsA.
Several genetic risk markers (HLA associations) are associated with development and variable prognosis in PsA.
Progression to PsA among patients with psoriasis has been reported to occur at a rate of around 2% per year.
Episodic flares of the disease in addition to chronic, baseline joint inflammation.
Joint erosion / damage may accrue over time, with the potential for development of functional impairments.
Accepted CASPAR criteria (ClASsification criteria for Psoriatic ARthritis) are routinely used to classify patients with PsA for trials and studies and may also aid in diagnosis of patients. These include the presence of psoriasis skin lesions, a family history of psoriasis, nail lesions, dactylitis, absence of rheumatoid factor, and periarticular bone formation on radiographs, with a point system to grade each feature (refer to CASPAR criteria; see References).
ICD10CM: L40.59 – Other psoriatic arthropathy
SNOMEDCT: 33339001 – Psoriasis with arthropathy
Differential Diagnosis & Pitfalls
Rheumatoid arthritis (RA) – Symmetric polyarthritis; presentation, clinical course, and radiologic and serologic features are distinct from PsA (may be rheumatoid factor and anti-cyclic citrullinated peptide [anti-CCP] positive). The absence of DIP involvement, asymmetry, axial involvement, dactylitis, skin psoriasis, psoriatic nail disease, and radiography may help distinguish RA from PsA.
Gout – History of podagra, joint fluid from arthrocentesis demonstrating monosodium urate crystal should help to differentiate; gout and psoriasis / PsA may coexist, however.
Pseudogout – Chondrocalcinosis on radiographs and calcium pyrophosphate crystals on joint fluid examination.
Reactive arthritis – Would not expect the presence of psoriasis skin disease; associated with other symptoms such as preceding genitourinary symptoms, diarrheal illness, and skin findings such as keratoderma blenorrhagicum.
Ankylosing spondylitis – To be distinguished from axial disease in PsA; PsA tends to have an asymmetric involvement of the sacroiliac joints, formation of "jug-handle" nonmarginal syndesmophytes that are asymmetrically located, skip lesions along the spine (cervical > lumbar involvement).
Fibromyalgia – Diffuse widespread pain involving "tender point" soft tissue areas. Synovitis is not a component of fibromyalgia. It is important to distinguish enthesitis (inflammation at sites of tendon insertion into bone) from the tender points of fibromyalgia, eg, near the lateral epicondyle of the upper extremity. Fatigue may be common to both conditions. Stiffness may be reported but does not improve with activity.
Up to 30% of people who have psoriasis develop joint inflammation (arthritis) called psoriatic arthropathy or psoriatic arthritis. Most people develop psoriasis before developing psoriatic arthropathy. However, symptoms of arthritis can appear before psoriasis in about 15% of patients. Psoriatic arthropathy presents as joint pain, stiffness, and swelling. Psoriatic arthropathy commonly develops between the ages of 30 and 50.
Who’s At Risk
Risk factors for psoriatic arthropathy include a history of psoriasis and a family history of psoriatic arthropathy.
Signs & Symptoms
The symptoms of psoriatic arthropathy tend to get worse as time goes on. It can cause joints on one or both sides of the body to become painful, with swelling and redness. In darker skin colors, the redness may be harder to see. The symptoms are similar to those of rheumatoid arthritis, but individuals with psoriatic arthropathy are more likely to experience swollen fingers and toes, foot pain, and lower back pain.
Other signs and symptoms of psoriatic arthropathy include:
Pain and stiffness that is worse following long periods of inactivity, such as when getting up in the morning.
Swelling of tendons (tendonitis, tenosynovitis).
Joints that appear red or darker than the surrounding skin color and are warm, tender, and painful.
Fingers that appear swollen.
Nails that appear to pull away or separate from the nail bed (onycholysis).
Some with psoriatic arthropathy also develop eye symptoms, including dry eyes, foreign body sensation, and redness in the whites of the eyes.
To help ease the symptoms of psoriatic arthropathy:
Maintain a healthy weight, such as by eating a plant-based diet (whole grains, fruits, and vegetables).
Exercise regularly, particularly with activities that do not stress your joints (swimming, walking, and bicycling).
Avoid straining your joints.
Use hot and cold therapy to reduce swelling and pain.
Use over-the-counter pain relievers such as ibuprofen (Advil, Motrin) or naproxen sodium (Aleve).
Participate in stress-management techniques and support groups. Ask your health care provider, or contact the National Psoriasis Foundation at https://www.psoriasis.org/about-psoriatic-arthritis.
When to Seek Medical Care
Contact your health care provider if you have psoriasis and begin to develop joint pain.
You may be referred to both a dermatologist and a rheumatologist to control inflammation, pain, and discomfort.
Your dermatologist or rheumatologist may recommend and prescribe a range of treatments to reduce symptoms:
Steroid injections can quickly reduce inflammation.
Prescription-strength pain relievers can help, although there are side effects (stomach, liver, and kidney irritation).
Apremilast (Otezla) is an oral medication that is approved for the treatment of psoriasis and psoriatic arthropathy.
Medications called biologics treat psoriasis and psoriatic arthropathy by blocking certain actions of the immune system. They are injected under the skin (subcutaneously). These medications include TNF-alpha inhibitors (eg, etanercept [Enbrel], infliximab [eg, Remicade]), IL12/23 inhibitors (eg, ustekinumab [Stelara]), IL-23 inhibitors (eg, guselkumab [Tremfya], risankizumab [Skyrizi]), and IL-17 inhibitors (eg, secukinumab [Cosentyx], ixekizumab [Taltz]). These are expensive and may have serious side effects, including infection, immunosuppression, and cancer.
Janus kinase (JAK) inhibitors (eg, Tofacitinib) are another newer type of medication for psoriatic arthropathy.
Methotrexate (Trexall) is a pill taken weekly that can slow the progression of arthritis. If you take this medication, you will need to see a medical professional regularly to monitor for possible side effects, such as liver damage.