Background Hidradenitis suppurativa (HS) is a chronic recurrent skin follicular disease that usually presents with inflammatory lesions in the apocrine gland-bearing areas (axillar, inguinal and anogenital regions). Musculoskeletal symptoms such as inflammatory back pain, seronegative asymmetric oligoarthritis and enthesitis and radiological abnormalities (sacroiliitis, syndesmophytes, and erosions) have been scarcely reported among patients with HS, but the classification of these rheumatological features has never been fully addressed, and their nosology remains unknown.
Objectives The aim of the study was to nosogically characterize the rheumatological involvement in patients diagnosed with HS
Methods Prospective, multicentre study. All patients were recruited from tertiary care hospitals by rheumatologist and dermatologist investigators. Inclusion criteria were an established diagnosis of HS according to international criteria and a history of either arthritis, dactylitis, enthesitis or inflammatory back pain. Clinical and radiological features were recorded in a preformed data sheet over a 12month period.
Results From 87 HS patients screened for suspicion of inflammatory rheumatic conditions, 32 fulfilled inclusion criteria, 84% women, with a mean age of 39.7±8.0 years. HS was exclusive dermatological finding in 71% of cases, and was associated with acne conglobata, psoriasis or palmo plantar pustulosis in 15%, 12% and 12% of patients, respectively. Four patients had an inflammatory bowel disease, and 2 had history of anterior uveitis. Prevalence of HLA-B27 positivity, tested in 16 patients, was 46%. Twenty-three out of 32 patients were receiving antibiotics for HS, 22 were taking NSAIDs, and 6 were treated with TNF-α blockers. HS antedated the rheumatologic symptoms in 85% of patients with a mean time delay of 17.5 (±8.4) years, whereas it occurred after or concomitantly in 15% of cases (mean delay: 6.8±2.4 years). Sixteen patients had enthesitis, 72% and 19% had axial and peripheral involvement, respectively. Dactylitis and anterior chest wall pain were present in 12%, and 35% of cases, respectively. Two patients had aseptic osteitis. Radiographs of both the pelvis and the spine were obtained in 20 patients. Sacroiliitis was seen in 8 patients, and syndesmophytes in 2 patients. MRI of the sacroiliac joints and the spine were obtained in 15 and 10 patients, respectively. In the spine, active inflammatory lesions were observed in 3 out of 15 patients, whereas they were seen in the sacroiliac joints of 3 out of 10 patients. Different sets of criteria were used to assess the prevalence of Spondyloarthritis (SpA) in these patients. The Amor criteria, ESSG criteria and ASAS criteria were met by 44%, 60% and 41% patients, respectively.
Conclusions SpA appears to be a predominant phenotype among musculoskeletal inflammatory features in HS patients. The concomitant occurrence of skin and joint manifestations in some cases suggest that common pathogenic mechanisms underlie both SpA and HS.
Disclosure of Interest None Declared
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