Hidradenitis suppurativa (HS) is a long-term inflammatory skin condition characterized by recurring, painful nodules, abscesses, and scarring, typically in areas like the armpits and groin. These nodules form when blocked hair follicles rupture, causing intense inflammation under the skin. Although primarily a skin disease, HS is connected to inflammatory joint pain, indicating it is a systemic condition. This co-occurrence suggests a shared underlying process affecting both the skin and the joints.
Why HS Causes Joint Inflammation
HS is understood to be a systemic inflammatory disorder where immune system dysregulation extends beyond the skin. Inflammation is driven by the release of pro-inflammatory messengers, known as cytokines, throughout the body. Key cytokines, including tumor necrosis factor-alpha (TNF-alpha) and various interleukins (IL-17, IL-1β, and IL-23), are significantly overexpressed.
These circulating inflammatory proteins travel through the bloodstream, affecting tissues far removed from the skin. The same inflammatory pathways that damage skin tissue can target the synovial tissue lining the joints. This shared inflammatory environment increases the risk of developing inflammatory arthritis.
Distinguishing Specific HS-Related Joint Conditions
Systemic inflammation associated with HS increases the risk for specific rheumatological diagnoses, particularly inflammatory arthritis. The most common type of joint disease linked to HS is Spondyloarthritis (SpA), a group of inflammatory conditions primarily affecting the spine and larger joints.
Within the SpA category, Ankylosing Spondylitis (AS) and Psoriatic Arthritis (PsA) are seen more frequently in people with HS. AS primarily involves axial involvement, affecting the spine and sacroiliac joints. PsA and other peripheral arthritis types involve joints in the limbs, such as the knees and ankles. HS is considered a seronegative arthropathy, but it is not strongly associated with the genetic marker HLA-B27.
Identifying Key Symptoms and Affected Joints
The joint pain associated with HS presents as inflammatory pain. A defining characteristic is morning stiffness lasting more than 30 minutes, which improves with activity rather than rest. Patients often report pain that wakes them from sleep at night.
The locations of the joint pain align with patterns seen in Spondyloarthritis. The lower back, buttocks, and sacroiliac area are commonly affected due to axial involvement. Peripheral joints, including the knees and ankles, can also experience pain, swelling, and stiffness.
Treatment Approaches for HS-Associated Joint Pain
Managing joint pain alongside HS requires an integrated strategy focused on reducing systemic inflammation and preserving joint function. Pharmacological treatment targets the underlying shared inflammatory pathways.
Biologics, such as TNF inhibitors, are frequently used because they effectively treat both moderate to severe HS and associated inflammatory arthritis. These medications address inflammation in the skin and the joints simultaneously. For milder joint symptoms, nonsteroidal anti-inflammatory drugs (NSAIDs) may be used to reduce pain. Supportive care, including physical therapy, helps maintain mobility and strengthen muscles. The best outcomes are achieved when a dermatologist and a rheumatologist coordinate care.