Psoriatic Arthritis: Where Skin and Joints Connect

Psoriatic arthritis is an inflammatory joint disease that affects some people with psoriasis. The relationship between skin and joint disease has fascinated researchers for decades and has led to important treatment breakthroughs.

The Skin-Joint Link

About thirty percent of people with psoriasis develop psoriatic arthritis. The skin disease typically appears first, sometimes by many years, although a minority develop joint symptoms before skin findings. Severity in one does not predict severity in the other.

Patterns of Joint Involvement

Unlike rheumatoid arthritis, psoriatic arthritis can be asymmetric. Some patients have a single swollen finger or toe (dactylitis, sometimes called sausage digit). Others develop spine involvement, similar to ankylosing spondylitis. Nail changes are common.

Nail Findings

Pitting, ridging, separation from the nail bed, and discoloration are common in psoriatic arthritis. The presence of nail changes is more strongly associated with arthritis than skin involvement alone.

Enthesitis

Inflammation where tendons and ligaments attach to bone, called enthesitis, is a hallmark feature. Heel pain at the Achilles tendon insertion or at the bottom of the foot is common and can mimic plantar fasciitis.

Modern Treatment

Treatment has been revolutionized by biologic medications targeting tumor necrosis factor, interleukin 17, and interleukin 23. These can substantially improve both skin and joint disease. Conventional DMARDs and newer oral targeted medications also play important roles.

Coordinated Care

Patients benefit from coordination between dermatology and rheumatology, as the same medication may treat both aspects of disease. Cardiovascular risk is elevated and deserves attention. For thorough patient information, the Arthritis Foundation is an authoritative resource.