Psoriatic arthritis

Psoriatic arthritis (PsA) is a long-term inflammatory arthritis that may occur in some people affected by the autoimmune disease psoriasis.<ref name="Fitz2">Template:Cite book</ref><ref name="Andrews">Template:Cite book</ref> The classic features of psoriatic arthritis include dactylitis (sausage-like swelling of the fingers), skin lesions, and nail lesions.<ref name="Ritchlin2017"/> Lesions of the nails may include small depressions in the nail (pitting), thickening of the nails, and detachment of the nail from the nailbed.<ref name="Ritchlin2017"/> Skin lesions consistent with psoriasis (e.g., red, scaly, and itchy plaques) frequently occur before the onset of psoriatic arthritis but psoriatic arthritis can precede the rash in 15% of affected individuals.<ref name="Ritchlin2017"/> It is classified as a type of seronegative spondyloarthropathy.

Genetics are thought to be strongly involved in the development of psoriatic arthritis.<ref name="Ritchlin2017"/> Obesity and certain forms of psoriasis are thought to increase the risk.<ref name="Ritchlin2017"/>

Psoriatic arthritis affects up to 30% of people with psoriasis. It occurs in both children and adults.<ref name="Ritchlin2017">Template:Cite journal</ref> Some people with PsA never get psoriasis.<ref name="auto3">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The condition is less common in people of Asian or African descent. It affects men and women equally.<ref name="Ritchlin2017"/> Template:TOC limit

Signs and symptoms

The signs and symptoms of psoriatic arthritis are very variable from one individual to the next.<ref name="Rossi2024" /> Symptoms usually appear after age 30.<ref name="Lembke2024" />

Peripheral joints

The majority of patients with PsA experience peripheral joint involvement.<ref name="pmid20015187" /> Pain, swelling, or stiffness in one or more joints is commonly present in psoriatic arthritis.<ref name="pmid20015187">Template:Cite journal</ref> Psoriatic arthritis is inflammatory, and affected joints are generally red or warm to the touch.<ref name="pmid20015187" /> Asymmetrical oligoarthritis, defined as inflammation affecting two to four joints during the first six months of disease, is present in 70% of cases. However, in 15% of cases, the arthritis is symmetrical.

The joints of the hand that are involved in psoriasis are the proximal interphalangeal, the distal interphalangeal, the metacarpophalangeal joint, and the wrist. Involvement of the distal interphalangeal joints is a characteristic feature in many cases.<ref name=":1">Template:Cite book</ref>

Sausage-like swelling in the fingers or toes, known as dactylitis, occurs in about 40% of PsA cases.<ref name="pmid20015187" /><ref name="arthritis.org">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

PsA may cause shoulder pain, most commonly felt in the front of the shoulder or the upper part of the arm. It is usually felt when moving the arm and may only be noticed in certain movements. In addition, many people find it painful when lying on the sore side in bed at night.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Axial skeleton (spine)

Approximately 25–70% of PsA patients have inflammation of the axial skeleton.<ref>Template:Cite journal</ref> There are also post inflammatory changes.<ref name="Rossi2024" /> Axial pain can occur in the area of the sacrum (the lower back, above the tailbone),<ref name="pmid20015187" /> as a result of sacroiliitis or spondylitis, which is present in 40% of cases.Template:Medical citation needed The inflammatory pain in the axial skeleton is worse in the early hours of the day.<ref name="Rossi2024" /> The pain is not relieved by resting, but rather by movement.<ref name="Rossi2024" /> The pain may be located in only part of the spine or sacroiliac joints, and may radiate to the legs down to the level of the back of the knee.<ref name="Rossi2024" /> It may be on both sides or only one side. There may also be stiffness and reduction of mobility in the spine. There are no symptoms in 20% of people with axial involvement.<ref name="Rossi2024" /> Over time, the spine may undergo ankylosis.<ref name="Rossi2024" />

Nails

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} Nail psoriasis (also termed psoriatic onychopathy) occurs in 80 to 90% of PsA cases. When PsA affects the finger joints, usually the distal interphalageal joint is involved, which is the joint closest to the nail.<ref name="Muneer2024">Template:Cite book</ref> The changes in the nails may only be very minimal, such as minor pits of the nail surface.<ref name="Ruderman2023">Template:Cite book</ref> The nails may be discolored (e.g., "oil spots").<ref name="Muneer2024" /> There may be subungual (under the nail) hyperkeratosis. The nail may separate from the nail bed, which is termed onycholysis.<ref name="Muneer2024" />

Psoriasis (skin)

Psoriasis classically presents with scaly skin lesions, which are most commonly seen over extensor surfaces such as the scalp, natal cleft, and umbilicus.Template:Medical citation needed Plaque-like psoriasis (psoriasis vulgaris) is the most frequent type of psoriasis in persons with PsA, but other types of psoriasis skin lesions are possible.<ref name="Rossi2024" /> 20-30% of people with psoriasis develop PsA.<ref name="Scalcon2025">Template:Cite journal</ref>

Enthesitis

Enthesitis is inflammation of an enthesis (the site where a tendon or ligament attaches to a bone). In PsA, enthesitis most often occurs at the attachment of the calcaneal tendon (Achilles tendon).<ref name="Pignon2025" /> It may also occur at the epicondyles of the elbow, plantar fascia, tendon of the quadriceps muscle, patella (knee bone), iliac crest (part of the hip), rotator cuff attachment, or supraspinatus attachment.<ref name="Rossi2024" /><ref name="Pignon2025" /><ref name="Ritchlin2017" />

Enthesitis is sometimes considered as a hallmark sign of PsA.<ref name="Pignon2025" /> Sometimes it may appear before any other sign of PsA or be the only sign of the disease.<ref name="Rossi2024" /> The same person may have multiple sites with enthesitis.<ref name="Pignon2025" /> Overall, enthesitis occurs in 42% of people with PsA.<ref name="Pignon2025" /> However, this figure varies significantly from 6% to 72% in reports.<ref name="Pignon2025" /> Enthesitis in PsA is associated with more active disease and the coexistence of fibromyalgia.<ref name="Pignon2025" />

Enthesitis, if present, may cause pain over a wider area around the joint.<ref name="auto4">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="arthritis.org"/> Pain can also occur in and around the feet and ankles, especially if there is enthesitis in the Achilles tendon or plantar fasciitis in the sole of the foot.<ref name="pmid20015187" />

Fatigue

Severe fatigue is present in approximately 30% of patients with PsA.<ref>Template:Cite journal</ref> It is sometimes described as extreme exhaustion that does not go away with adequate rest. The fatigue may be caused directly by the disease itself, or be a secondary effect of other factors.<ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref>

Poor sleep quality is common among people with psoriatic arthritis.<ref>Template:Cite journal</ref>

Psychological

PsA is associated with anxiety and depression. People with the condition may have reduced participation in social activity and become socially isolated.<ref name="Rossi2024" /><ref name="Pignon2025">Template:Cite journal</ref>

Pattern of disease activity

Psoriatic arthritis may remain mild or may progress to more destructive joint disease. Periods of active disease, or flares, will typically alternate with periods of remission. In severe forms, psoriatic arthritis may progress to arthritis mutilans<ref name=DAVIDSONS2010>Template:Cite book</ref> which on X-ray gives a "pencil-in-cup" appearance.<ref name="Ritchlin2017"/>

Complications

Rare complications are uveitis in one or both eyes, slightly higher risk of heart conditions, and increased risk of Crohn's disease and of non-alcoholic fatty liver disease (NAFLD).<ref name="auto4"/> Other potential comorbidities which may occur together with PsA include hypertension (high blood pressure), obesity, diabetes, metabolic syndrome, cardiovascular disease, fibromyalgia, osteoporosis, and infections.<ref name="Rossi2024" />

While people with psoriasis have a slightly increased risk of cancer (especially lymphoma and keratinocyte cancer),<ref name="Vaengebjerg2020" /> there is very limited evidence available about any possible link between PsA and cancer. From available evidence, there does not appear to be any increased risk of cancer, apart perhaps from breast cancer.<ref name="Vaengebjerg2020">Template:Cite journal</ref>

Causes

Psoriatic arthritis is an inheritable polygenic disease, with many genes known or theorized to contribute to its clinical presentation (or lack thereof). When someone with the genes for psoriatic arthritis comes into contact with certain substances, these substances may induce an autoimmune reaction, causing the immune system to target normal tissues in the body. The exact strength, location, and clinical effects of this reaction depend on which genes are involved for each individual. The substance that triggers the reaction is typically not known.<ref name="Ritchlin2017" />

Genomic analysis has identified several genes involved in some patients, notably genes related to class I MHC including HLA-B*08, HLA-B*27, HLA-B*38, and HLA-B*39. Other genes relating to the immune system and central tolerance may also be involved, such as interleukin receptor genes. Thematically, these genes are often those that identify human tissues as normal and healthy, or the genes in immune cells designed to recognize those identifiers. In the case of psoriatic arthritis, the genes targeting immune cells are overexpressed, which leads to an increase in the recruitment of phagocytic neutrophils present in psoriatic skin lesions, hereby increasing inflammation and phagocytosis of healthy cells.<ref name="Billi 2020">Template:Cite journal</ref> If the genes are functioning abnormally, then the immune system has a higher risk of attacking normal tissues.<ref name="Ritchlin2017" />

Bone cells such as osteoclasts are theorized to be involved in patients with psoriatic arthritis, in contrast to most people with psoriasis whose bone cells are not significantly involved in the disease.<ref>Template:Cite journal</ref>

HLA-B27

Approximately 40–50% of individuals with psoriatic arthritis have the HLA-B27 genotype.<ref name="Ritchlin2017"/> Whilst the incidence of psoriatic arthritis is significantly higher among people positive for HLA-B27 (compared to the overall population), the vast majority of people with HLA-B27 will not have psoriatic arthritis.<ref name="auto1">Template:Cite book</ref> For instance in the US HLA-B27 incidence is 6-8%,<ref name="auto1"/> whilst psoriatic arthritis incidence has been estimated at 0.06–0.25%.<ref name="auto">Template:Cite journal</ref>

Risk factors

Health and environmental factors known to be associated with psoriatic arthritis include:<ref name="Ritchlin2017" />

• Current, or history of, severe psoriasis
• Disease of the finger/toenails
• Obesity
• Tissue trauma, or deep lesions associated with sites of trauma
• Smoking.<ref name="Vaengebjerg2020" />
• Alcohol.<ref name="Vaengebjerg2020" />

Diagnosis

There is no definitive test to diagnose psoriatic arthritis. Several classification criteria have been proposed, but they have wide variability.<ref name="auto"/> A rheumatologist (a physician specializing in autoimmune diseases) may use physical examinations, health history, blood tests, and X-rays to accurately diagnose psoriatic arthritis.

Factors that contribute to a diagnosis of psoriatic arthritis include the following:

• Psoriasis in the patient, or a family history of psoriasis or psoriatic arthritis.
• A negative test result for rheumatoid factor, a blood factor associated with rheumatoid arthritis.
• Arthritis symptoms in the distal interphalangeal articulations of hand (the joints closest to the tips of the fingers). This is not typical of rheumatoid arthritis.
• Ridging or pitting of fingernails or toenails (onycholysis), which is associated with psoriasis and psoriatic arthritis.
• Radiologic images demonstrating degenerative joint damage.

Other symptoms that are more typical of psoriatic arthritis than other forms of arthritis include enthesitis (inflammation in the Achilles tendon (at the back of the heel) or the plantar fascia (bottom of the feet)), and dactylitis (sausage-like swelling of the fingers or toes).<ref name="jh">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Enthesitis also occurs in axial spondyloarthritis.<ref name="Pignon2025" />

Imaging

• Psoriatic arthritis digit ar1934-2.gif

  T2-weighted MRI (sagittal) of index finger in PsA (mutilans form) showing probable erosion (increased signal) at base of the middle phalanx (long thin arrow), synovitis at the proximal interphalangeal joint (long thick arrow), soft tissue edema (short thick arrow), and diffuse bone edema (short thin arrows) of the proximal phalanx.

• Psoriatic arthritis dactylitis ar1934-4.gif

  T1 weighted axial MRIs of the fingers in PsA. (a) Pre- and (b) post-contrast showing dactylitis due to flexor tenosynovitis at the second finger with enhancement and thickening of the tendon sheath (large arrow), and synovitis at proximal interphalangeal joint (small arrow).

• Psoriatic arthritis spine ar1934-6.gif

  (a) T1-weighted and (b) STIR MRI of lumbar and lower thoracic spine in PsA showing active inflammation at several levels (arrows), anterior spondylitis at L1/L2, and an inflammatory Andersson lesion at the upper vertebral endplate of L3.

• Sacroiliitis MRI ar1934-5.gif

  T1-weighted semi-coronal MRI of sacroiliac joints (a) before and (b) after contrast showing active sacroiliitis (arrow).

• Psoriatic arthritis fingers ar1934-1.gif

  Coronal T1-weighted MRI of fingers in PsA. (a) Pre- and (b) post-contrast showing active synovitis at proximal and distal interphalangeal joints (large arrows), joint space narrowing, bone proliferation at proximal interphalangeal joint, erosions at distal interphalangeal joint (white circle), enthesitis medial to proximal interphalangeal joints.

• Psoriatic arthritis ankle ar1934-3.gif

  (a) STIR Sagittal MRI of ankle showing enthesitis at Achilles tendon insertion (thick arrow), synovitis of ankle joint (long thin arrow), and bone marrow edema at tendon insertion (short thin arrow). T1 weighted images, before (b) and after (c) contrast show enthesitis (large arrow) and bone erosion at tendon insertion (short thin arrows).

Differential diagnosis

Several conditions can mimic the clinical presentation of psoriatic arthritis including rheumatoid arthritis, osteoarthritis, reactive arthritis, gouty arthritis, systemic lupus erythematosus, and inflammatory bowel disease-associated arthritis.<ref name="Ritchlin2017"/>

In contrast to psoriatic arthritis, rheumatoid arthritis tends to affect the proximal joints (e.g., the metacarpophalangeal joints), involves a greater number of joints than psoriatic arthritis, and affects them symmetrically.<ref name="Ritchlin2017"/> Involvement of the spinal joints is more suggestive of psoriatic arthritis than rheumatoid arthritis.<ref name="Ritchlin2017"/> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="auto2">Template:Cite journal</ref>

Comorbidities may help differential diagnosis.<ref name="auto2"/>

Osteoarthritis shares certain clinical features with psoriatic arthritis such as its tendency to affect multiple distal joints in an asymmetric pattern.<ref name="Ritchlin2017"/> Unlike psoriatic arthritis, osteoarthritis does not typically involve inflammation of the sacroiliac joint.<ref name="Ritchlin2017"/>

Psoriatic arthritis sometimes affects only one joint and is sometimes confused for gout or pseudogout when this happens.<ref name="Ritchlin2017"/>

Classification

PsA itself may be classified both as a type of arthropathy (a condition affecting the joints) and as a type of spondyloarthritis / spondyloarthropathy (inflammation of the joints in the spine).<ref name="Rossi2024" />

There are five main types of psoriatic arthritis:<ref name="Ritchlin2017"/><ref name=jh/>

• Oligoarticular: This type affects around 70% of patients and is generally mild. This type does not occur in the same joints on both sides of the body and usually only involves fewer than 3 joints.
• Polyarticular: This type accounts for around 25% of cases, and affects five or more joints on both sides of the body simultaneously. This type is most similar to rheumatoid arthritis and is disabling in around 50% of all cases.
• Arthritis mutilans (Template:ICD10): Affects less than 5% of patients and is a severe, deforming, and destructive arthritis. This condition can progress over months or years causing severe joint damage. Arthritis mutilans has also been called chronic absorptive arthritis and may be seen in rheumatoid arthritis.
• Spondyloarthritis (Template:ICD10): This type is characterized by stiffness of the neck or the sacroiliac joint of the spine, but can also affect the hands and feet, in a similar fashion to symmetric arthritis.
• Distal interphalangeal predominant (Template:ICD10): This type of psoriatic arthritis is found in about 5% of patients and is characterized by inflammation and stiffness in the joints nearest to the ends of the fingers and toes. Nail damage is often marked.

Management

Because prolonged inflammation can lead to joint damage, early diagnosis and treatment to slow or prevent joint damage is recommended.<ref name="pmid20461787">Template:Cite journal</ref>

The underlying process in psoriatic arthritis is inflammation; therefore, treatments are directed at reducing and controlling inflammation. The first-line initial treatment for most patients is a TNF inhibitor-type biological disease-modifying anti-rheumatic drug (DMARD).<ref>Template:Cite journal</ref><ref name=":1" />

The goal of treatment is to achieve minimal or low disease activity. The criteria for minimal disease activity is meeting five of these seven criteria and low disease activity/remission is achieved when all seven criteria are fulfilled: (1) tender joint count ≤1, (2) tender entheseal joints ≤1, (3) swollen joint count ≤1, (4) PASI ≤1 or BSA ≤3%, (5) patient pain VAS ≤15, (6) patient global disease activity VAS ≤20, (7) HAQ ≤0.5.<ref>Template:Cite journal</ref>

Biological DMARDs

Biologics (also called biological response modifiers) are a class of therapeutics developed using recombinant DNA technology. Biologic medications are derived from living cells cultured in a laboratory. Unlike traditional DMARDs that affect the entire immune system, biologics target specific parts of the immune system. They are given by injection or intravenous (IV) infusion.

Biologics prescribed for psoriatic arthritis are TNF-α inhibitors, including infliximab, etanercept, golimumab, certolizumab pegol and adalimumab, as well as the IL-12/IL-23 inhibitor ustekinumab,<ref name="Ritchlin2017" /> the IL-17A inhibitor secukinumab,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and the IL-23 inhibitor risankizumab.

Biologics may increase the risk of minor and serious infections.<ref>Template:Cite book</ref> More rarely, they may be associated with nervous system disorders, blood disorders or certain types of cancer.Template:Citation needed People with psoriasis who are treated with biologics do not have a higher risk of cancer.<ref name="Vaengebjerg2020" />

Nonsteroidal anti-inflammatory drugs

Typically the medications first prescribed for psoriatic arthritis are NSAIDs such as ibuprofen and naproxen, followed by more potent NSAIDs like diclofenac, indomethacin, and etodolac. NSAIDs can irritate the stomach and intestine, and long-term use can lead to gastrointestinal bleeding.<ref name="pmid10377455">Template:Cite journal</ref><ref name="pmid3085490">Template:Cite journal</ref> 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.<ref name=AHA>Template:Cite journal</ref><ref name=BMJ>Template:Cite journal</ref> Both COX-2 inhibitors and other non-selective NSAIDs have potential adverse effects that include damage to the kidneys.

Conventional synthetic disease-modifying antirheumatic drugs

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. Most DMARDs act slowly and may take weeks or even months to take full effect.<ref>Template:Cite journal</ref> According to a recent Cochrane review, low dose oral methotrexate was slightly more effective than placebos.<ref>Template:Cite journal</ref> Immunosuppressant drugs can also reduce psoriasis skin symptoms but can lead to liver and kidney problems and an increased risk of serious infection.Template:Citation needed

Phosphodiesterase-4 inhibitors

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. By inhibiting PDE4, an enzyme that breaks down cyclic adenosine monophosphate, cAMP levels rise, resulting in the down-regulation of various pro-inflammatory factors including TNF-α, interleukin 17 and interleukin 23, as well as the up-regulation of anti-inflammatory factor interleukin 10.

It is given in tablet form and taken by mouth. Side effects include headaches, back pain, nausea, diarrhea, fatigue, nasopharyngitis, and upper respiratory tract infections, as well as depression and weight loss.

It was patented in 2014 and manufactured by Celgene. There is no current generic equivalent available on the market.

JAK inhibitors

The JAK1 inhibitors tofacitinib (Xeljanz) and upadacitinib (Rinvoq) are approved for the use in active psoriatic arthritis.<ref>Template:Cite journal</ref> 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.<ref name=:0>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Takeda has also initiated a Phase III, Multicenter, Randomized, trial to evaluate the efficacy and safety of TAK-279 in subjects with Moderate-to-Severe Plaque Psoriasis.<ref name=":0" /><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Other treatments

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.<ref>Template:Cite journal</ref>

Photochemotherapy with methoxsalen and long-wave ultraviolet light (PUVA therapy) are used for severe skin lesions. Doctors may use joint injections with corticosteroids in cases where one joint is severely affected. In psoriatic arthritis patients with severe joint damage orthopedic surgery may be implemented to correct joint destruction, usually with the use of a joint replacement. Surgery is effective for pain alleviation, correcting joint disfigurement, and reinforcing joint usefulness and strength.

Management of fatigue

Changes in lifestyle may help manage fatigue.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Prognosis

The condition can be disabling,<ref name="Rossi2024" /> severely decreasing physical health.<ref name="Lubrano2025">Template:Cite journal</ref> People with PsA may have reduced ability to work.<ref name="Rossi2024" /> Psychological health may also be decreased as a result of chronic pain, anxiety, depression, and reduced self esteem.<ref name="Lubrano2025" /> As a result, quality of life may also be significantly reduced.<ref name="Lubrano2025" /> Some of the possible comorbidities (conditions which may occur together with PsA) may reduce life span.<ref name="Rossi2024" />

Epidemiology

A 2024 systematic review reported the global prevalence of adults with PsA as 0.112% (112 per 100 000 adults).<ref name="Lembke2024">Template:Cite journal</ref> Reported prevalence ranges from 0.1 to 1% of the general population.<ref name="Rossi2024" /> The reason for the wide variation is possibly related to different genetics, environmental factors such as lifestyle and diet, and the methods used in the research (e.g., definition and method of detection).<ref name="Rossi2024" /> The disease is more common in some populations. In Europe, the prevalence is 0.188% (188 per 100,000), 0.048% (48 per 100,000) in Asia, 0.133% (133 per 100,000) in North America, and 0.017% (17 per 100,000) in South America.<ref name="Lembke2024" /> Other studies found an overall prevalence rate of 0.1-0.2%, and an incidence rate of 0.006% annually.<ref name="auto1"/> Males and females are affected in equal proportion.<ref name="Lembke2024" /> The peak incidence (number of new cases) happens between the ages of 30 and 60.<ref name="Lembke2024" />

70% of people who develop psoriatic arthritis first show signs of psoriasis on the skin, 15% develop skin psoriasis and arthritis at the same time, and 15% develop skin psoriasis following the onset of psoriatic arthritis.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Some people with PsA never get psoriasis.<ref name="auto3"/>

Psoriatic arthritis can develop in people who have any level severity of psoriatic skin disease, ranging from mild to very severe.<ref>Who's At Risk, Be Joint Smart (a coalition of the National Psoriasis Foundation and the Arthritis Foundation). Accessed 2016-11-12.</ref> Studies have found that obesity is a significant risk factor and predictor of disease outcome.<ref name=":2">Template:Cite journal</ref> Other risk factors associated with an increased risk of developing psoriatic arthritis include severe psoriasis, nail psoriasis, scalp psoriasis, inverse psoriasis, and having a first-degree relative with psoriatic arthritis.<ref name=":0" />

Psoriatic arthritis tends to appear about 10 years after the first signs of psoriasis.<ref name="Ritchlin2017"/> For the majority of people, this is between the ages of 30 and 55, but the disease can also affect children. The onset of psoriatic arthritis symptoms before symptoms of skin psoriasis is more common in children than adults.<ref name="Psoriatic Arthritis on Medscape">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

More than 80% of patients with psoriatic arthritis will have psoriatic nail lesions characterized by nail pitting, separation of the nail from the underlying nail bed, ridging and cracking, or more extremely, loss of the nail itself (onycholysis).<ref name="Psoriatic Arthritis on Medscape" /><ref name="auto"/>

Men and women are equally affected by this condition.<ref name="Ritchlin2017"/> Like psoriasis, psoriatic arthritis is more common among Caucasians than African or Asian people.<ref name="Ritchlin2017"/>

Prevention

Some progress has been made in preventing patients with psoriasis from developing psoriatic arthritis. However, once psoriatic arthritis is established, the inflammatory burden of psoriatic disease might not be susceptible to modulation in many patients.<ref>Template:Cite journal</ref>

External links

• Psoriatic Arthritis at Patient.info
• Guidelines of care for the management of psoriasis and psoriatic arthritis—National Guideline Clearinghouse
• US National Institute of Arthritis and Musculoskeletal and Skin Diseases