[12] Axial pain can occur in the area of the sacrum (the lower back, above the tailbone),[5] as a result of sacroiliitis or spondylitis, which is present in 40% of cases.

[13] Nail pitting often accompanies distal interphalangeal joint involvement and may be essential in differentiating psoriatic arthritis from other diseases.

[14] Psoriasis classically presents with scaly skin lesions, which are most commonly seen over extensor surfaces such as the scalp, natal cleft, and umbilicus.

[16][17][18] A small (n=247) 2023 study found poor sleep quality was common among patients with psoriatic arthritis.

[22] Psoriatic arthritis is an inheritable polygenic disease, with many genes known or theorized to contribute to its clinical presentation (or lack thereof).

[23] If the genes are functioning abnormally, then the immune system has a higher risk of attacking normal tissues.

[22] A rheumatologist (a physician specializing in autoimmune diseases) may use physical examinations, health history, blood tests, and X-rays to accurately diagnose psoriatic arthritis.

[3] Rheumatoid factor (RF) and cyclic citrullinated peptide autoantibodies are typically found in the blood of people with RA, but not, as a rule, in those with PsA.

[27] Osteoarthritis shares certain clinical features with psoriatic arthritis such as its tendency to affect multiple distal joints in an asymmetric pattern.

The first-line initial treatment for most patients is a TNF inhibitor-type biological disease-modifying anti-rheumatic drug (DMARD).

[34][35] Coxibs (COX-2 inhibitors) e.g. celecoxib or etoricoxib, are associated with a statistically significant 50 to 66% relative risk reduction in gastrointestinal ulcers and bleeding complications compared to traditional NSAIDs, but carry an increased rate of cardiovascular events such as myocardial infarction (MI) or heart attack, and stroke.

Oral small molecules such as methotrexate, leflunomide, cyclosporin, azathioprine, and sulfasalazine are used in persistent symptomatic cases without exacerbation.

Rather than just reducing pain and inflammation, this class of drugs helps slow down or halt the progression of the disease, and therefore limit the amount of joint damage that occurs.

[38] According to a recent Cochrane review, low dose oral methotrexate was slightly more effective than placebos.

[39] Immunosuppressant drugs can also reduce psoriasis skin symptoms but can lead to liver and kidney problems and an increased risk of serious infection.

[citation needed] A first-in-class treatment option for the management of psoriatic arthritis is apremilast, a small molecule phosphodiesterase-4 inhibitor approved for use by the FDA in 2014.

Side effects include headaches, back pain, nausea, diarrhea, fatigue, nasopharyngitis, and upper respiratory tract infections, as well as depression and weight loss.

[40] The TYK2 inhibitor deucravacitinib (Sotyktu), which has been approved for plaque psoriasis, is currently undergoing a Phase II clinical trial to evaluate the efficacy and safety on psoriatic arthritis.

The Takeda TYK2 inhibitor TAK-279 recently demonstrated a 20% improvement in signs and symptoms of disease at week 12 as compared to placebo in a Phase II clinical trial.

[41] Takeda also plans to initiate a Phase III clinical trial to evaluate the efficacy and safety of TAK-279.

[41] A review found tentative evidence of benefit of low level laser therapy and concluded that it could be considered for relief of pain and stiffness associated RA.

[42] Photochemotherapy with methoxsalen and long-wave ultraviolet light (PUVA therapy) are used for severe skin lesions.

[48][22] Enthesitis is observed in 30 to 50% of patients and most commonly involves the plantar fascia and Achilles’ tendon, but it may cause pain around the patella, iliac crest, epicondyles, and supraspinatus insertions[49] Men and women are equally affected by this condition.