Psoriasis as a comorbidity of hidradenitis suppurativa

Hidradenitis suppurativa (HS) and psoriasis (PSO) appear to share important pathogenic elements; in spite of this, the co-occurrence of the two has been widely unexplored.

To explore the co-occurrence of HS and PSO, we recorded the number of patients attending the outpatient clinic at the Department of Dermatology, Zealand University Hospital, Roskilde, Denmark, for the ICD10 diagnosis HS (DL73.2) or PSO (DL40.0, DL40.3, DL40.4, DL40.8, and DL40.9). Data were further compared with previously reported Danish national prevalence rates for HS and PSO.

A total of 1,036 patients were included from the outpatient clinic: 440 HS, 624 PSO, and 28 with both diagnoses. In total 6.4% of HS patients had PSO, and 4.5% of PSO patients had HS. HS patients had OR = 2.99 (95% CI 2.04-4.38) of having PSO as compared to the background population. For PSO patients, they had OR = 2.56 (95% CI 1.74-3.77).

We found a strong association between HS and PSO, which implies a possible comorbidity between PSO and HS that has not previously been properly elucidated. Such a connection could be a common inflammatory pathway driven by the increased secretion of IL-12/23 and TNFα that is a hallmark of both diseases.