A 19-year-old male suffered from concomitant AF and HS for 3.5 years. His mother and aunt 58 had HS, his maternal grandmother was affected with rheumatoid arthritis. AF appeared 1 59 month after isotretinoin treatment prescribed for doxycycline-resistant acne. HS appeared 1 60 month later, after oral steroid initiation. The following treatments, prescribed for AF and HS, 61 failed: isotretinoin, oral steroids for 4 months combined first with isotretinoin for 2 months 62 then with tetracycline for 2 months, zinc, nonsteroidal anti-inflammatory drugs, rifampin-63 clindamycin combination, alone for 5 months, then associated with infliximab for 7 months 64 and with adalimumab for 5 months. 65

At first examination, the patient had lost 11 kg and had a low-grade fever. He could not sit 66 nor walk, because of pain in HS lesions, shoulders, elbows and ankles (8/10 on a visual 67 analogic scale). He presented with erosions and crusts over his face and back (Fig1), Hurley 68 stage 3 HS lesions in one axilla and Hurley 2 lesions in all other HS areas (Fig 2). 69 Before treatment, biology showed increased levels of the following blood tests: C-reactive-70 protein (CRP= 140mg/l), erythrocyte-sedimentation-rate (ESR= 102mm), white blood cell and 71 neutrophil count (11800 and 8300/mm3, respectively), TNFα (33pg/ml for N< 20pg/ml), IL6 72 (25pg/ml for N< 8pg/ml), with normal serum IL1β and negative HLA-B27. Normal 17α-OH-73 progesterone level excluded adrenal hyperplasia. Bacterial cultures revealed after 7 days a 74 polymorphous anaerobic flora (predominantly Prevotella and Porphyromonas spp) with 75