A 13-year-old girl who was left completely bald from her alopecia has made an incredible transformation after taking an arthritis drug.

The unidentified teenager, from Brazil, had slowly been losing her hair for five years and standard medications failed to help. Doctors tried tofacitinib as a last-resort.

Tests of the drug, marketed as Xeljanz, have shown it can help alopecia patients regrow their hair – but it is not yet licensed as a conventional treatment.

After just four months, the girl regained a significant amount of her hair. She was left with thick, brown locks within two years of taking tofacitinib.

The results add to the evidence that the drug could offer hope for millions of patients around the world with alopecia, who have slim chances of making a full recovery.

Tofacitinib is routinely given to patient with rheumatoid arthritis, which is caused by inflammation. Dermatologists say the type of alopecia the girl had is caused by the same process.

Medical student Rachel Berbert Ferreira, at Centro Universitario Cesumar, was the senior author of the paper in Clinical Case Reports.