Low Risk of Inflammatory Arthritis in Hidradenitis Suppurativa Patients Save

JAMA Dermatology reports that after the onset and diagnosis of hidradenitis suppurativa (HS), such patients have a higher risk of certain forms inflammatory arthritis.

Using commercial claims data identified 70 697 patients with a diagnosis of HS from a dermatologist or more than one health care professional. Patients with preexisting inflammatory arthritis, including ankylosing spondylitis, psoriatic arthritis, rheumatoid arthritis, etc. were excluded. 

HS patients were compared to 141412 risk-set matched patients without HS. The median follow-up was 1.5 years, with a maximum of 11 years and both groups were free of arthritis prior to entry.

After propensity score matching, patients with HS had an increased risk for developing:

• ankylosing spondylitis - the incidence rate was 0.60 vs 0.36 per 1000 (HR, 1.65 [95% CI, 1.15-2.35])
• psoriatic arthritis (incidence rate, 0.84 vs 0.58 per 1000; HR, 1.44 [95% CI, 1.08-1.93])
• rheumatoid arthritis (incidence rate, 4.54 vs 3.86 per 1000; HR, 1.16 [95% CI, 1.03-1.31])

Thus there seems to be an increased risk of developing ankylosing spondylitis, psoriatic arthritis, and rheumatoid arthritis among patients with HS compared with those without HS.   Yet the risk of arthritis is low, with a resultant increase of only 2 to 6 additional cases per 10 000 patients with HS per 1.5 years.