Hidradenitis suppurativa (HS) is a difficult disease to treat. Although the 
pathogenesis of this inflammatory skin disease is largely unknown, the important 
role of the immune system has been demonstrated in both experimental and 
clinical studies. Clinicians are therefore increasingly prescribing systemic 
treatments with immunosuppressive agents, but the more traditionally used 
systemic retinoids, especially isotretinoin, also remain relatively common 
therapies. In order to provide an overview of all currently available systemic 
immunosuppressive agents and retinoids for the treatment of HS, a systematic 
search was performed using the Medline and Embase databases. All published 
papers concerning systemic retinoids or immunosuppressive treatments for HS in 
adults were included. The primary endpoints were the percentages of significant 
responders, moderate responders and nonresponders. Other endpoints were the 
relapse rate and adverse events. In total 87 papers were included, comprising 
518 patients with HS who were treated with systemic retinoids, biological agents 
or another immunosuppressive agents, including colchicine, ciclosporin, dapsone 
or methotrexate. The highest response rates were observed with infliximab, 
adalimumab and acitretin. Overall, the quality of evidence was low and differed 
between the agents, making direct comparisons difficult. However, based on the 
amount of evidence, infliximab and adalimumab were the most effective agents. 
Acitretin was also effective in HS, although the quality of the evidence was 
low. The therapeutic effect of isotretinoin is questionable. Randomized 
controlled trials are needed to confirm the effectiveness of acitretin, and to 
identify the most effective immunosuppressive agents in HS.