Background:Ustekinumab is a new immunosuppressive anti-psoriasis agent. The drug targets the p40 subunit of IL-12 and IL-23 and indirectly inhibits cytokine production by Th17 cells.Main observations:We present a case of a 36-year-old male patient with psoriasis, who received ustekinumab therapy, applied in 45mg subcutaneous injections at week 0, 4 and than every 12 weeks. After 7 months of therapy PASI decreased from 10,1 to 0,9. At this phase of therapy he developed two patches of alopecia areata on the scalp. The diagnosis was made based on clinical appearance and was confirmed by trichoscopy (hair and scalp dermoscopy) and reflectance confocal microscopy. The development of alopecia areata was preceded by emotional stress and dental infection. Conclusions:Ustekinumab seems an unlikely cause of alopecia areata in this patient. However, lack of efficacy is preventing hair loss may indicate that interleukin- 12 cytokine family is not a key player in pathogenesis of alopecia areata.