Psoriatic Arthritis

Psoriasis of the skin or nails may precede or follow joint involvement. Severity of the joint and skin disease is often discordant. Also, skin lesions may be hidden in the scalp, ears, gluteal folds, or umbilicus and go unrecognized by the patient.

Peripheral psoriatic arthritis may involve small, medium, and large joints with a high tendency to affect distal interphalangeal joints of fingers and toes. It may manifest in different patterns such as asymmetric oligoarthritis, symmetric polyarthritis (which can be confused with rheumatoid arthritis), and arthritis mutilans that is characterized by rapid destructive arthritis with telescoping of the digits.

Joint and skin symptoms may lessen or worsen simultaneously. Inflammation of the flexor tendons of fingers, toes, or both may lead to sausage-shaped deformities (dactylitis), which are not present in patients with rheumatoid arthritis Rheumatoid Arthritis (RA) Rheumatoid arthritis is a chronic systemic autoimmune disease that primarily involves the joints. Rheumatoid arthritis causes damage mediated by cytokines, chemokines, and metalloproteases.... read more . Rheumatoid nodules are absent. Arthritic remissions tend to be more frequent, rapid, and complete than in rheumatoid arthritis, but progression to chronic arthritis and crippling may occur.

Enthesopathy (inflammation at tendinous insertion into bone—eg, Achilles tendinitis, patellar tendinitis, elbow epicondyles, spinous processes of the vertebrae) can develop and cause pain and swelling.

Axial involvement may be present, especially in male patients with positive HLA-B27, and usually manifests as asymmetric involvement of the sacroiliac joints.

Psoriatic arthritis should be suspected in patients with both psoriasis and arthritis. Because psoriasis may be overlooked or hidden or develop only after arthritis occurs, psoriatic arthritis should be considered in any patient with seronegative inflammatory arthritis, particularly with involvement of distal interphalangeal joints, asymmetric or lower spine involvement, or presence of enthesitis and/or dactylitis: these patients should be examined for psoriasis and nail pitting and should be questioned about a family history of psoriasis. Patients suspected of having psoriatic arthritis should be tested for RF. Occasionally, RF test results can be positive. However, anticyclic citrullinated peptide antibodies (anti-CCP) are highly specific for rheumatoid arthritis Rheumatoid Arthritis (RA) Rheumatoid arthritis is a chronic systemic autoimmune disease that primarily involves the joints. Rheumatoid arthritis causes damage mediated by cytokines, chemokines, and metalloproteases.... read more and are only rarely present in psoriatic arthritis.

Psoriatic arthritis is diagnosed clinically and by excluding other disorders that can cause such similar manifestations. X-ray findings common in psoriatic arthritis include distal interphalangeal joint involvement; resorption of terminal phalanges and cupping of proximal phalanges; arthritis mutilans; and extensive destruction, proliferative bone reaction, a sausage-like appearance to digits, and dislocation of large and small joints. The main distinguishing features from rheumatoid arthritis, in addition to the presence of psoriasis, include findings of dactylitis, joint asymmetry, distal interphalangeal and sacroiliac joint involvement, and more prominent enthesitis.

Treatment of psoriatic arthritis is directed at controlling skin lesions Treatment Psoriasis is an inflammatory disease that manifests most commonly as well-circumscribed, erythematous papules and plaques covered with silvery scales. Multiple factors contribute, including... read more and at reducing joint inflammation. A treat-to-target approach to achieve full disease remission or minimal disease activity has been suggested and can be assessed at each visit by using the disease activity index for psoriatic arthritis (DAPSA) or minimal disease activity (MDA) scores (1 Treatment references Psoriatic arthritis is a seronegative spondyloarthropathy and chronic inflammatory arthritis that occurs in people with psoriasis of the skin or nails. The arthritis is often asymmetric, and... read more , 2 Treatment references Psoriatic arthritis is a seronegative spondyloarthropathy and chronic inflammatory arthritis that occurs in people with psoriasis of the skin or nails. The arthritis is often asymmetric, and... read more ).

Drug therapy has been similar to that for rheumatoid arthritis Rheumatoid Arthritis (RA) Rheumatoid arthritis is a chronic systemic autoimmune disease that primarily involves the joints. Rheumatoid arthritis causes damage mediated by cytokines, chemokines, and metalloproteases.... read more , particularly using the DMARD Traditional disease-modifying antirheumatic drugs (DMARDs) Rheumatoid arthritis is a chronic systemic autoimmune disease that primarily involves the joints. Rheumatoid arthritis causes damage mediated by cytokines, chemokines, and metalloproteases.... read more methotrexate, although clinical trial data have shown inconsistent results in psoriatic arthritis. Hydroxychloroquine is inconsistently of benefit and may cause exfoliative dermatitis or aggravate underlying psoriasis. Benefit may be gained from nonsteroidal anti-inflammatory drugs Nonsteroidal anti-inflammatory drugs (NSAIDs) Rheumatoid arthritis is a chronic systemic autoimmune disease that primarily involves the joints. Rheumatoid arthritis causes damage mediated by cytokines, chemokines, and metalloproteases.... read more , cyclosporine, TNF-alpha antagonists, ustekinumab, secukinumab, ixekizumab, tofacitinib, abatacept, and guselkumab (see Biologic agents Biologic agents Rheumatoid arthritis is a chronic systemic autoimmune disease that primarily involves the joints. Rheumatoid arthritis causes damage mediated by cytokines, chemokines, and metalloproteases.... read more ). TNF-alpha antagonists have been particularly effective.

Methotrexate 10 to 15 mg orally once/week (with folic acid 1 mg orally once/day) is given. If tolerated but not adequate, the dosage of methotrexate is increased after 3- to 5-week intervals to a maximum of 25 mg orally or by injection once/week (oral bioavailability decreases above 15 mg in a single dose). In some patients, skin is more responsive than the joints to methotrexate.

Sulfasalazine is usually given as enteric-coated tablets. Benefit should occur within 3 months. Enteric coating or dose reduction may increase tolerability. Because neutropenia may occur early, complete blood count (CBC) should be obtained after 1 to 2 weeks and then about every 12 weeks during therapy. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) should be obtained at about 6-month intervals and whenever the dose is increased. Response has been inconsistent.

Apremilast is a phosphodiesterase-4 inhibitor that is effective for psoriasis and psoriatic arthritis. The initial dosage is 10 mg orally once/day, titrated to the maintenance dose of 30 mg orally twice a day as tolerated. Adverse effects include diarrhea, nausea, headache, depression, and weight loss. Skin is often more responsive to this medication than the joints.

Tumor necrosis factor (TNF)-alpha antagonists (eg, adalimumab, etanercept, golimumab, certolizumab pegol, infliximab, and their biosimilars) reduce the progression of joint damage (see rheumatoid arthritis treatment Treatment Rheumatoid arthritis is a chronic systemic autoimmune disease that primarily involves the joints. Rheumatoid arthritis causes damage mediated by cytokines, chemokines, and metalloproteases.... read more for more details about TNF inhibitors). TNF inhibitors occasionally paradoxically trigger psoriaform reactions including plaque, palmoplantar pustular, and guttate psoriasis.

Ustekinumab is an interleukin (IL)-12 and IL-23 antagonist. The dosage is 45 mg subcutaneously at weeks 0 and 4 (loading dosages) followed by 45 mg every 12 weeks thereafter. The dosage is 90 mg subcutaneously if the patient weighs > 100 kg. Adverse effects are similar to those of the other biologic agents Biologic agents Rheumatoid arthritis is a chronic systemic autoimmune disease that primarily involves the joints. Rheumatoid arthritis causes damage mediated by cytokines, chemokines, and metalloproteases.... read more .

Guselkumab is an anti-IL-23-specific monoclonal antibody that is effective in treating moderate to severe psoriasis and has shown to be effective in treating psoriatic arthritis as well. It is given by subcutaneous injections at a recommended dose of 100 mg at weeks 0 and 4 and every 8 weeks thereafter.

Secukinumab is an IL-17 inhibitor. Secukinumab can be given at a dosage of 150 mg subcutaneously at weeks 0, 1, 2, 3, and 4 and every 4 weeks thereafter. Without the loading (weekly) dosage, secukinumab is given at 150 mg subcutaneously every 4 weeks. ​If patients continue to have active psoriatic arthritis, a dose of 300 mg should be considered. ​Secukinumab may be given with or without methotrexate. Adverse effects include urticaria, upper respiratory infections, fungal infections due to Candida, diarrhea, herpes zoster, and worsening inflammatory bowel disease.

Ixekizumab is an IL-17A inhibitor. It is indicated for adults with moderate-to-severe plaque psoriasis who are candidates for systemic therapy or phototherapy as well as for adults with active psoriatic arthritis. It may be given alone or in combination with a conventional DMARD (eg, methotrexate). The dosage is 160 mg subcutaneously (two 80-mg injections) at week 0, followed by 80 mg subcutaneously every 4 weeks. Ixekizumab increases the risk of upper respiratory infections and fungal infections and has also been associated with worsening symptoms of inflammatory bowel disease.

Tofacitinib is an oral Janus kinase (JAK) inhibitor. It is available for adults with active psoriatic arthritis who have had an inadequate response to or who are intolerant of methotrexate or other DMARDs. The dosage is 5 mg orally 2 times a day. The extended-release dosage is 11 mg orally once/day. Potential adverse effects include risk of infection, particularly varicella-zoster virus reactivation, increased creatinine levels, neutropenia, venous thromboembolic events, and hyperlipidemia. See Rheumatoid Arthritis: Treatment Treatment Rheumatoid arthritis is a chronic systemic autoimmune disease that primarily involves the joints. Rheumatoid arthritis causes damage mediated by cytokines, chemokines, and metalloproteases.... read more for more details about major cardiovascular adverse events and malignancies with JAK inhibitors (3 Treatment references Psoriatic arthritis is a seronegative spondyloarthropathy and chronic inflammatory arthritis that occurs in people with psoriasis of the skin or nails. The arthritis is often asymmetric, and... read more ).

Abatacept is a soluble fusion cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) Ig. It is available for adults with active psoriatic arthritis and can be used with or without a nonbiologic DMARD (eg, methotrexate, sulfasalazine, hydroxychloroquine, leflunomide). It may be given as an IV infusion or as a subcutaneous injection. For the IV infusion, the dose is weight adjusted as follows: 500 mg for patients weighing < 60 kg, 750 mg for patients weighing 60 to 100 kg, and 1 g for patients weighing > 100 kg. After the initial dosage, abatacept should be given at weeks 2 and 4 and every 4 weeks thereafter. The subcutaneous injection dosage is 125 mg once/week. Adverse effects include pulmonary toxicity, susceptibility to infection, headache, upper respiratory infection, sore throat, and nausea.