Psoriatic arthritis

Definition

Psoriatic arthritis is an immune-mediated (autoimmune), connective tissue disease that is associated with a skin disorder marked by bumps and scaling (psoriasis) and is characterized by inflammation of the ligaments, tendons, fascia, and joint capsules (enthesitis) of the upper extremities, especially the hands. Small joints of the feet and large joints of the legs such as hips, knees, and ankles may be also involved. Most commonly, psoriatic arthritis affects fewer than five joints. Its arthroscopic symptoms and clinical findings are similar to those of rheumatoid arthritis, but it differs in its high frequency of distal joint involvement (joints farthest from the center of the body, such as small joints of hands and feet) and the serum of affected individuals is negative for rheumatoid factor.

Psoriatic arthritis occurs in five general patterns: arthritis affecting the small distal joints of toes and fingers (distal interphalangeal arthropathy), asymmetrical oligoarticular arthritis of the extremities, symmetrical polyarthritis that resembles rheumatoid arthritis, deforming and destructive arthritis (arthritis mutilans) with resorption of bone (osteolysis) and dissolution of the joint, and arthritis of the spine and sacroiliac joints (psoriatic spondylitis). These patterns may change in an individual over time.

The etiology of psoriatic arthritis is unknown, but genetic, immunologic and less conclusively, environmental factors such as infection and trauma are considered important components. The disease is associated with increased frequency of certain human leukocyte antigens (including HLA-B27, HLA-DR4m -DR7, and –Cw6) in the tissue of those affected with psoriasis and/or psoriatic arthritis. Genome scans have shown linkages to specific gene loci. Serum levels of immunoglobulins (IgA and IgG) are higher in psoriatic arthritis patients. Psoriasis is present years before the onset of arthritis in about 70% of individuals with psoriatic arthritis; 10% to 15% develop psoriasis and arthritis simultaneously, and 15% to 20% have arthritis before skin involvement (Ruderman). Risk: Individuals with psoriasis are at greatest risk for developing psoriatic arthritis; approximately 5% to 8% of individuals with psoriasis develop psoriatic arthritis (Hammadi). In contrast to rheumatoid arthritis, which affects women more than men, psoriatic arthritis shows no gender preference. Psoriatic arthritis usually occurs in individuals between ages 35 and 55 years, but can develop at any age. Risk is greater among whites than other races. A family history of psoriatic arthritis is a risk factor for developing the disease. Incidence and Prevalence: Incidence of psoriatic arthritis in the general population is estimated to be 1%; about 1 million adults in the US are affected (Hammadi) compared to 2 million with rheumatoid arthritis (Hammadi). Although incidence varies among countries, the incidence of psoriatic arthritis internationally ranges from 1% to 40% depending on the clinical criteria applied and whether all races are included (Van Voorhees). Prevalence is higher among whites than among African Americans and Native Americans; the disease occurs in 2.5% of white North Americans and 0.05% to 0.24% in the international white population (Hammadi).

Source: Medical Disability Advisor

Diagnosis

History: The individual may describe a family history of psoriasis or psoriatic arthritis. The individual may complain of pain, stiffness, and swelling of the joints, especially the small joints of the hands and feet. Depending on the area affected by psoriatic arthritis, other complaints may include back pain, chest pain, pain on walking or climbing stairs, pain around the eyes, and shortness of breath. Humidity and temperature changes may affect arthritis symptoms. Fever may be present in patients with the arthritis mutilans subtype of psoriatic arthritis. Individual may report that psoriasis has been present for some time before arthritis symptoms or that psoriasis developed at the same time as arthritis symptoms. The physician will obtain a history of recent and prior illness, particularly bacterial or viral infections. Physical exam: Psoriasis is usually present but may be limited to patches (lesions) between the buttocks, behind the ears, or other inconspicuous areas such as the umbilicus or scalp; psoriasis can be severe in some individuals. Swelling may be seen as well as deformity of the joints, especially finger joints in severe, chronic cases. Overgrowth of bone (hyperostosis) may be seen. "Sausage digits" (dactylitis) of the hands and feet are common in individuals with psoriatic arthritis. Affected joints often have a purplish discoloration. An accumulation of fluid may be seen in a joint (effusion). Nails of the affected digits may be pitted or crumbling (onycholysis). Inflammation of the outer membrane of the eyes (conjunctivitis) or the uveal tract (uveitis) may occur in up to 30% of individuals with psoriatic arthritis (Van Voorhees). Tests: There is no specific diagnostic test for psoriatic arthritis; observing the pattern of joint involvement is essential to correct diagnosis. Blood tests that may be helpful in making the diagnosis include erythrocyte sedimentation rate and C-reactive protein to evaluate inflammation, hemoglobin, rheumatoid factor (to rule out rheumatoid arthritis), uric acid (to rule out gout), human leukocyte antigen (HLA) typing, and antinuclear antibodies. A sample of joint fluid may be analyzed to determine the number and type of white blood cells. A cytokine profile may be done to assess T cell and monocyte activation, which may help differentiate between psoriatic arthritis and rheumatoid arthritis. X-rays usually are done to help differentiate psoriatic arthritis from other types of arthritis based on degree of joint erosion. Depending on areas affected and symptoms reported by the individual, either CT or MRI imaging can be done to examine soft tissue and joint characteristics in more detail. CT scans of the sacroiliac joint are considered to be sensitive for viewing spondylitis or sacroiliitis. MRI is especially sensitive for assessing pathology of the hands and feet.

Treatment

Treatment of the polyarthritis component focuses on controlling inflammation. It is subdivided into nonpharmacological, pharmacological, and surgical therapies. Nonpharmacological therapies include rest, wearing of splints over the affected joints, joint protection, and physical therapy. Pharmacological measures include nonsteroidal/anti-inflammatory drugs (NSAIDs), occasional corticosteroid injections into the joints, disease modifying antirheumatic drugs (DMARDs), and newer, injectable biologic agents that target tissue necrosis factor (TNF) and other cytokines. Surgery (hip or knee replacement) may be indicated in severe cases.

The psoriasis component is treated with topical therapy, systemic medications, and photochemotherapy (psoralen plus UV light). Treatment is individualized and depends on the size and location of psoriasis plaques. Immunosuppressive drugs (e.g., methotrexate) and retinoic-acid derivatives may be given in cases of severe skin involvement. These drugs have demonstrated effectiveness for both skin and joint symptoms. Cyclosporine, an antibiotic, has also demonstrated good results for psoriasis and psoriatic arthritis although it has toxic effects in some individuals.

Exercise is an important component of a treatment plan for psoriatic arthritis, resulting in reduced pain, swelling, and stiffness. Sufficient rest is also required.

Source: Medical Disability Advisor

Prognosis

Many individuals with psoriatic arthritis have mild disease with episodic flares and remissions. Because psoriatic arthritis is a chronic disease, joint deformities and movement limitations may increase over time. However, most individuals can maintain reasonable function of the affected joints. Medication can lead to periods of symptom remission. Individuals with many affected joints (polyarthritis), a family history of arthritis, early onset (younger than 20 years of age), or severe skin psoriasis have a poorer prognosis. Inflammatory arthritis of the spine (spondylitis) may develop in some individuals. Some will progress to a severe stage characterized by joint disintegration (lysis) or immobility (ankylosis).

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