Diagnosis of Rheumatoid Arthritis Leaves Individuals Predisposed to Developing Hidradenitis Suppurativa, Study Finds

A study seeking to evaluate the bidirectional association between hidradenitis suppurativa (HS) and rheumatoid arthritis (RA) found that patients with a history of RA are more susceptible to developing HS, according to results published in Immunologic Research.

The current population-based study enrolled 6779 patients with HS and 33,260 age-, sex- and ethnicity-matched control subjects. Investigators used a case study design to evaluate the prevalence of preexisting RA among patients with HS and identify the odds of RA in individuals with a history of HS, as well as a retrospective cohort design to assess the risk of RA after HS.

Results of the case-controlled design showed the following:

• The prevalence of preexisting RA was greater among patients with HS relative to controls (0.5% vs 0.3%, respectively; P = .019). 
• The odds of being diagnosed with HS were found to be 1.6-fold higher in patients with a history of RA (odds ratio [OR], 1.59; 95% CI, 1.07-2.36).
• In an age-, sex-, and ethnicity-stratified analysis, the association of RA with subsequent HS was greater among individuals older than 40 years (OR, 1.73; 95% CI, 1.08-2.79; P = .022), men (OR, 2.22; 95% CI, 1.01-4.89; P = .041), and Arab individuals (OR, 2.93; 95% CI, 1.15-7.45; P = .018).
• The association between a history of RA and a later diagnosis of HS was only significant in individuals in whom the diagnosis of RA preceded that of HS by more than 10 years (OR, 1.99; 95% CI, 1.09-3.63; P = .022).
• After carrying out a multivariate analysis adjusting for putative confounders, the association was robust to a model adjusting for age and sex (age- and sex- adjusted OR, 1.61; 95% CI, 1.08-2.38; P = .019), as well as to a model adjusting for age, sex, ethnicity, body mass index (BMI), and comorbidities (fully adjusted OR, 1.66; 95% CI, 1.11-2.49; P = .014).

Results of the retrospective cohort design showed the following:

• The incidence rate of RA was estimated at 4.3 (95% CI, 2.5-6.8) and 2.4 (95% CI, 1.8-3.2) cases per 10,000 person-years in patients with HS and controls, respectively.
• The unadjusted risk of RA was numerically, but not statistically, higher in patients with HS relative to controls (HR, 1.75; 95% CI, 0.99-3.90; P = .055).
• In a stratified analysis, the risk of RA was only elevated in individuals older than 30 years (HR, 1.94; 95% CI, 1.02-3.69; P = .043).
• The risk of RA in HS fell short of significance after adjusting for age and sex (age- and sex-adjusted HR, 1.75; 95% CI, 0.99-3.09; P = .055) as well as for age, sex, ethnicity, BMI, and comorbidities (fully adjusted HR, 1.45; 95% CI, 0.77-2.72; P = .249).

An assessment of the characteristics of patients with HS and comorbid RA relative to the remaining patients with HS elucidated that patients with HS and comorbid RA were significantly older at the onset of HS, had greater Charlson Comorbidity Index scores, and had higher lifetime prevalence of diabetes mellitus, hypertension, and hyperlipidemia.

The risk of all-cause mortality was found to be comparable between the 2 subgroups following an evaluation of all-cause mortality of patients with HS and comorbid RA compared with the remaining patients with HS (HR, 2.59; 95% CI, 0.64-10.47; P = .183).

The findings of the current study should bring awareness to clinicians managing patients with HS and RA about the association between the diseases and their respective symptoms. Treatment methods that have demonstrated positive results for both conditions might be preferred for patients with a dual diagnosis of HS and RA. More research is needed to understand the underlying pathomechanisms of the study’s observations, authors concluded.

Reference

Kridin K, Shavit E, Damiani G, Cohen AD. Hidradenitis suppurativa and rheumatoid arthritis: evaluating the bidirectional association. Immunol Res. 2021;69(6):533-540. doi:10.1007/s12026-021-09221-4