Baricitinib-Induced Trichilemmal Cyst Reactivation in a Woman With Alopecia Areata

A case study from a Spanish hospital reported the reactivation of trichilemmal cysts in a 53-year-old woman with alopecia areata (AA) after treatment with baricitinib, a Janus kinase inhibitor. The patient, who had a history of trichilemmal cysts and had previously failed other treatments, achieved total hair regrowth by week 8 of baricitinib treatment. However, 6 weeks into the treatment, 4 trichilemmal cysts reactivated on her scalp. This side effect, not previously reported, may be linked to the drug's mechanism of inhibiting the Janus kinase/signal transducer and activator of transcription pathway, which could reactivate hair follicles and cysts. The study suggests considering personal and family history of trichilemmal cysts before starting baricitinib for AA.