Pathobiology Questions Raised by Telogen Effluvium and Trichodynia in COVID-19 Patients

The document reports on a study involving 39 patients in Italy who experienced telogen effluvium (TE), a form of hair loss, and trichodynia, a painful sensation of the scalp, after contracting COVID-19. The patients, consisting of 9 men and 30 women aged between 48 and 73 years (mean age 64.6), developed symptoms 8 weeks to 3 months following the onset of COVID-19. Laboratory tests showed normal thyroid function, iron, ferritin, and vitamin B12 levels. The study suggests that the systemic hyperinflammatory response to COVID-19, known as the "cytokine storm," is likely responsible for inducing TE, as cytokines such as IL-6, TNFa, IL-1B, and IFNg promote the transition of hair follicles to the catagen phase. Additionally, the study raises the possibility that COVID-19 may impact the expression of olfactory receptors in hair follicles, which are involved in hair growth, and explores the potential role of ACE2 receptors in hair follicle biology. The findings indicate that hair loss and trichodynia resolved within 2 to 4 months and highlight the need for further research to develop targeted therapeutic strategies for hair loss associated with COVID-19.