Derm Dx: Plaques, joint deformity of the hands

There are 7 million individuals in the United States with psoriasis, and psoriatic arthritis will develop in 5% to 42% of those people.1 The wide range in those affected is the result of the variable methods used to diagnose psoriatic...

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There are 7 million individuals in the United States with psoriasis, and psoriatic arthritis will develop in 5% to 42% of those people.¹ The wide range in those affected is the result of the variable methods used to diagnose psoriatic arthritis, with many individuals unaware of their condition.

Psoriatic arthritis can occur before (15%), concurrent with (10%), or after (75%) the presentation of psoriasis. Men and women are affected equally, and the peak age of diagnosis is 30 to 50 years.²

Psoriatic arthritis is a multifactorial condition with genetic, environmental, and immunologic factors. Although the exact pathogenesis is unknown, certain human leukocyte antigen types and antigens (such as streptococcal) are associated with an increased risk for the development of psoriatic arthritis.³

The clinical presentation of psoriatic arthritis most commonly involves oligoarthritis of the distal phalanges. Although there is no universally accepted classification of psoriatic arthritis, the Moll and Wright criteria is frequently used to divide psoriatic arthritis into subclasses.³ There is significant overlap in the subclasses, and disease may switch from one subclass to another or be classified into multiple subclasses. The subclasses are as follows:⁴

• asymmetric oligoarthritis, involving fewer than 5 joints;

• symmetric polyarthritis, involving greater than 5 joints and similar in presentation to rheumatoid arthritis (87% have negative rheumatoid factor);

• distal arthritis, involving the distal interphalangeal joints;

• mutilating arthritis, a destructive form of psoriatic arthritis that results in severe deformity; and

• spondyloarthropathy, which affects mainly the spine, with or without peripheral arthritis.

In addition to the arthritis, patients may present with tenosynovitis, enthesitis, and dactylitis. Enthesitis is inflammation of the insertion points of tendons and ligaments and commonly involves the plantar fascia, Achilles tendon, and ribs and vertebra. Dactylitis is swelling of the tendons and ligaments of the entire finger. It is often called “sausage digit” and occurs in 30% of patients.⁵

Nail changes occur in 90% of those with psoriatic arthritis, including pitting, thickening, onycholysis, and subungual hyperkeratosis. In fact, nail involvement is the most important factor in determining whether psoriatic arthritis will develop in the future in a person with psoriasis.²

To improve the diagnosis of psoriatic arthritis, highly sensitive and specific criteria were developed based on an international study. In the CASPAR (ClASsification of Psoriatic ARthritis) criteria, a patient must have inflammatory articular disease with 3 or more points from the following 5 categories:³

• Evidence of psoriasis: 2 points if current, 1 point if present in past or family history

• Nail involvement: 1 point

• Negative test for rheumatoid factor: 1 point

• Dactylitis (current or past): 1 point

• Radiographic evidence of juxtaarticular new bone formation (excluding osteophyte): 1 point

The goals of treatment are to improve patient quality of life, provide relief from symptoms, and limit further progression and damage. Mild disease is treated with nonsteroidal anti-inflammatory agents and glucocorticoids.⁴ For more severe forms of disease, disease-modifying antirheumatic drugs should be added to the treatment. Anti-tumor necrosis factor drugs are also effective to treat psoriatic arthritis and are especially useful in refractory disease.

Nagalakshmi Nagarajan, BS, is a medical student at the University of Texas Medical School at Houston, and Maura Holcomb, MD, is a resident at Baylor College of Medicine in Houston, Texas.

References

1. Gelfand JM, Gladman DD, Mease PJ, et al. Epidemiology of psoriatic arthritis in the population of the United States. J Am Acad Dermatol. 2005;53(4):573.
2. Mease P, Goffe BS. Diagnosis and treatment of psoriatic arthritis. J Am Acad Dermatol. 2005;52(1):1-19.
3. Wright V, Moll JM. Psoriatic arthritis. Bull Rheum Dis. 1971;21(5):627-632.
4. Ruderman EM, Tambar S. Psoriatic arthritis: prevalence, diagnosis, and review of therapy for the dermatologist. Dermatol Clin. 2004;22(4):477-486.
5. Taylor W, Gladman D, Helliwell P, et al. Classification criteria for psoriatic arthritis: development of new criteria from a large international study. Arthritis Rheum. 2006;54(8):2665-2673.