Clinical Context

Inflammatory diseases can certainly mimic one another, and sometimes they can even be influenced by the same pathologic mechanisms. The authors of the current study previously examined a connection between hidradenitis suppurativa (HS) and Crohn disease (CD) among adults, and their results were published in the July 2018 issue of JAMA Dermatology.^[1] They noted that both HS and CD are chronic inflammatory disorders of epithelia that are colonized by commensal flora. They share clinical pathological features of suppuration and sinus tract formation, and both HS and CD share pathology of the interleukin-23/T-helper cell type 17 pathway as well as tumor necrosis factor (TNF). Hidradenitis suppurativa and CD are usually first diagnosed among young people, and smoking is associated with a worse prognosis in both HS and CD.

The cross-sectional study examined 51,340 adults with HS, and it found that 2% of these patients had concomitant CD. Risk factors for a higher rate of CD were White race, age 45 to 64 years, no history of obesity, and tobacco smoking. In multivariable analysis, the hazard ratio for CD associated with HS was 3.05 (95% CI: 2.87, 3.25). Crohn disease was associated with a higher risk for CD across all patient subgroups, regardless of race, age, sex, smoking status, or the presence of obesity.

To date, there has been no similar research examining the relationship between HS and CD among adolescents. Previous research was limited to small case studies but still found that the prevalence of CD was 2 times higher among pediatric patients with HS vs among pediatric patients without HS. The current study by Mastacouris and colleagues used larger case and control groups to address the relationship more definitively between HS and CD among pediatric patients.

Study Synopsis and Perspective

There appears to be an association between CD and HS among pediatric patients, but the absolute prevalence is low.

Methodology

• Researchers drew from the IBM Explorys database, which includes electronic health records from > 40 US healthcare networks, to evaluate the prevalence of CD among pediatric patients with HS, an association that has been found in adults.
• The population included 2883 patients aged 12 to 17 years who were diagnosed with HS between January 1, 2015 and December 31, 2019, on the basis of International Classification of Diseases, Ninth Revision or International Classification of Diseases, 10th Revision codes and 222,186 age-matched control persons who had not been diagnosed with HS.
• The primary outcome was a CD diagnosis on or before December 31, 2019.
• The researchers used unadjusted and adjusted log-binomial regression models to describe the crude association between HS and CD and to address potential confounders.

Takeaway

• In the unadjusted analysis, the prevalence of CD was 0.69% among patients with HS and 0.17% among control persons.
• In the adjusted analysis, the CD prevalence ratio was 4.9 times higher among patients with HS compared with control persons (P < .001).
• In a subgroup analysis of patients aged 15 to 17 years that was adjusted for covariates, the CD prevalence ratio was 4.84 times higher among patients with HS compared with control persons (P < .001).

In Practice

• This cross-sectional study is too preliminary to have practice applications; "however, the low absolute prevalence of CD in this group is reassuring and should be taken into context when counseling patients," the researchers concluded.

Study Details

• Amit Garg, MD, of the department of dermatology at the Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, New Hyde Park, New York, led the research. The study was published as a research letter in JAMA Dermatology.^[2]

Limitations

• The database lacked details on disease severity and duration, and the researchers were unable to determine causality.

Implications for the Healthcare Team

• Hidradenitis suppurativa and CD share pathologic features of suppuration and sinus tract formation, and both HS and CD share pathology of the interleukin-23/T-helper cell type 17 pathway as well as tumor necrosis factor. Hidradenitis suppurativa and CD are usually first diagnosed among young people, and smoking is associated with a worse prognosis in both HS and CD. In a previous study by Garg and colleagues, the presence of HS was associated with a 3-fold increase in the prevalence of CD among adults.
• The current study by Mastacouris and colleagues found that the presence of HS among adolescents was associated with nearly a 5-fold increase in the prevalence of CD. This relationship was particularly strong among adolescents between the ages of 15 and 17 years.
• When counseling adolescent patients with HS, members of the healthcare team should discuss the fact that while associations with CD have been identified, the low absolute prevalence of CD in the study group is reassuring.

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