Unexpected Effect of Baricitinib Use: Observation of a Case of Hypertrichosis

March 2026 in “ Indian Journal of Dermatology ”

Marco Greco, Camilla Chello, Maria Cristina Acri, Alfredo Rossi, Teresa Grieco, Giovanni Pellacani

baricitinib JAK1/2 inhibitor alopecia areata hypertrichosis JAK/STAT pathway Wnt/β-catenin pathway hair follicle dynamics

TLDR Baricitinib can cause excessive hair growth.

A case study of a 48-year-old woman with alopecia areata treated with baricitinib, a JAK1/2 inhibitor, revealed an unexpected side effect of hypertrichosis, or excessive hair growth, in areas such as the forehead, cheeks, and neck. While baricitinib is effective in promoting hair regrowth in alopecia areata by modulating the JAK/STAT pathway, this is the first documented instance of it causing hypertrichosis. The study suggests that the drug's influence on the Wnt/β-catenin pathway, which is involved in hair follicle dynamics, may explain this side effect.

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