For clinicians at the intersection of dermatology and rheumatology, the link between inflammatory dermatoses and articular involvement is well-established, most notably in the psoriasis-psoriatic arthritis spectrum. New data now strongly suggests that Hidradenitis Suppurativa (HS) shares a similar, though less clinically apparent, association with inflammatory arthritis. A recent study reveals compelling evidence of occult arthropathy in HS, underscored by a remarkably high prevalence of HLA-B27.
In a cohort of HS patients presenting with arthralgia, a striking 76% were found to be HLA-B27 positive. This finding alone is a significant signal towards a potential spondyloarthropathy-like phenotype. However, the clinical picture was deceptively benign; a formal swollen joint count was positive in only 12% of these patients, with a median count of zero. This discrepancy highlights the subclinical nature of the condition and the inadequacy of physical examination alone for assessment.
Both serological markers and advanced imaging modalities substantiated objective evidence of inflammation:
Elevated Inflammatory Markers: The HS cohort exhibited significantly higher median levels of C-reactive protein and erythrocyte sedimentation rate compared to both PsO and control groups, confirming a state of systemic inflammation.
Musculoskeletal Ultrasound (MSUS): While low-grade, greyscale synovitis was ubiquitous across all groups, the more specific finding of GS-tenosynovitis was detected in 32% of HS patients. This prevalence was comparable to that of the PsO cohort (36%) and substantially higher than in controls (12%). Power Doppler signal, however, was rare across all groups, indicating low-grade vascularization within the inflamed tissue.
Fluorescence Optical Imaging (FOI): Using the Xiralite method, FOI of the hands revealed significantly higher inflammatory enhancement in HS patients compared to both PsO patients and controls. This points to a distinct and more intense inflammatory signature in the small joints of the hand in the HS population.
The confluence of high HLA-B27 prevalence, elevated inflammatory markers, and definitive imaging evidence of tenosynovitis and synovitis—in the absence of significant clinical swelling—builds a robust case for a true, yet occult, inflammatory arthritis in HS. These findings necessitate a paradigm shift in how we evaluate arthralgia in our patients with HS. For definitive characterization, we must look beyond the physical examination and employ imaging to objectify the underlying pathology.
#HidradenitisSuppurativa #Dermatology #Rheumatology #OccultArthritis #Spondyloarthropathy #HLAB27 #MedicalImaging #DermRheum