Does COVID19 cause permanent hair loss? — Donovan Hair Clinic
Some patients with COVID19 have fibrosis and nerve thickening
A new study showed that patients with hair shedding issues after COVID-19 had dermal fibrosis and thickened nerve trunks. These observations open the possibility that some amount of hair loss could be permanent although more studies are needed to confirm this hypothesis.
Michelini et al. 2023
In a recent study, authors set out to better understand the features of post COVID telogen effluvium
They evaluated four female patients aged between 53 and 62 years of age with acute hair loss starting 1-3 months after COVID 19 infection. Pull test was positive in these four patients. Trichoscopy (hair demoscopy) showed typical TE patterns: regrowing hairs, single follicular units, empty hair follicles(HFs) and thin terminal hairs.
Trichogram showed telogen rate higher than 20%.
Surprising Biopsy Findings
Biopsies showed hair follicles median anagen/telogen ratio was 50% (normal 90:10%). No inflammatory infiltrate was present. Interestingly, a wide variety of histological features were present. This included different stages of dystrophic changes including bulb atrophy up and fibrosis. The authors also observed that the presence of thickened nerve trunks or hypertrophy of nerve endings (also called dermal hyperneury) was a defining and nearly pathognomonic feature seen in all of the 4 patients.
Summary and Conclusion
Dermal hyperneury has been defined as the presence of increased and hypertrophic myelinated and nonmyelinated nerve fibers in the dermis. There is an exaggerated size and prominence of dermal nerve fibers. “Dermal hyperneury” affects sensory C fibers. It has been described in pain syndromes like postherpetic neuralgia.
Here the authors found that dermal hypertrophy may be part of COVID shedding.
The authors here describe that fibrosis may also be part of the COVID related telogen effluvium. They proposed that the “cytokine storm” that occurs in the course of Sars-Cov2 can trigger fibrosis. The authors discuss the possibility that the dermal fibrosis seen in post COVID shedding could potentially cause a permanent reduction in hair density in susceptible patients and that more study is needed.
All in all, more study is needed to understand how sensory issues resolve in post COVID shedding and whether fibrosis leads to a reduction in density or regrowth potential.
Michelini S et al. Telogen Effluvium in SARS-CoV-2 Infection: histological aspects. J Eur Acad Dermatol Venereol. 2023 Mar 8.
Dr. Jeff Donovan is a Canadian and US board certified dermatologist specializing exclusively in hair loss.
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