Azathioprine in hidradenitis suppurativa with inflammatory phenotype: a case series of 11 patients

Hidradenitis suppurativa (HS) is a chronic inflammatory disease that negatively impacts the quality of life of patients. It presents as deep-seated nodules, abscesses, fistulae, sinus tracts, and scars in the axilla, inguinal area, submammary folds, and perianal area. Recently, two phenotypes have been described: a follicular phenotype and an inflammatory phenotype. Numerous medical treatments are available for hidradenitis suppurativa, with particular importance of antitumor necrosis factor antibodies. Due to the association of HS with other conditions with a pro-inflammatory state, particularly Crohn's disease, it has been suggested that azathioprine may have a role in the treatment of HS.

To assess the effectiveness of azathioprine monotherapy in patients with moderate-severe HS.

We retrospectively studied patients with HS treated with azathioprine in monotherapy. We performed both clinical and ultrasound evaluation at baseline as well as in the follow-up visits. Their baseline score on the iHS4 and DLQI scales and 12-16 weeks after starting the treatment were compared. We also registered the number of patients who achieved HiSCR.

Six patients presented significant improvement, reducing their score in iHS4 and DLQI scales and achieving HiSCR. Another patient had clinical improvement, meaning reduction in iHS4 and DLQI, but without achieving HiSCR. Two patients stopped the treatment before week 12 because of adverse events. The remaining two patients presented no improvement. The median (Q3-Q1) baseline iHS4 score was 6 (12-6), and follow-up iHS4 score, 4 (6-2), being these differences statistically significant (P = 0.006). Median (Q3-Q1) baseline DLQI scores and 12-16 weeks after treatment were 17 (23-11) and 14 (18-9) although statistically nonsignificant (P = 0.099).

We present a case series of 11 patients treated with azathioprine with good clinical and ultrasonographic response. We suggest that azathioprine may benefit a certain patient profile with the inflammatory phenotype.