Letter: Alopecia areata during ustekinumab administration: Co-existence or an adverse reaction?

Alopecia areata (AA) is a tissue-specific, T-cell-mediated autoimmune disease characterized by non-scarring hair loss. Ustekinumab is a human immunoglobulin monoclonal antibody that binds with the p40-subunit of interleukin-12 (IL-12) and IL-23 and has been licensed for the treatment of moderate to severe plaque psoriasis. The exact pathogenesis of AA remains unclear. However, increased Th1 serum cytokine levels have been associated with this condition. Thus, IL-12 inhibitors (ustekinumab) would be expected to treat or at least to prevent hair loss. We report two cases of acute AA occurring while on ustekinumab administration.