A migraine patient developed persistent hair loss at the fremanezumab injection site, adding to growing evidence that CGRP-blocking peptide drugs can cause localized alopecia by disrupting hair follicle immune protection.
Injection site alopeciaPersistent localized hair loss developed specifically at the fremanezumab injection site — a rarely reported pattern for CGRP inhibitors
What the researchers found
A patient using fremanezumab (a CGRP-blocking antibody for migraine prevention) developed persistent hair loss localized to the injection site on the lower extremity. This is notable because most reported CGRP inhibitor-related alopecia has been scalp-based and associated with erenumab, not fremanezumab.
The proposed mechanism is that blocking CGRP removes its immunomodulatory protection of hair follicles, causing the follicle's 'immune privilege' to collapse — essentially, the immune system attacks hair follicles that were previously shielded by CGRP signaling.
Why it matters
CGRP inhibitors are rapidly becoming first-line migraine prevention drugs, prescribed to millions of patients. While clinical trials showed few side effects, post-marketing reports of hair loss are accumulating. This case adds injection site-specific alopecia to the known pattern and proposes a mechanistic explanation rooted in CGRP's role in hair follicle immune privilege — important for understanding why this peptide-blocking therapy affects hair growth.
The numbers in context
1 patient · Fremanezumab injection · Lower extremity injection site · Persistent localized alopecia
How the study worked
This is a clinical case report documenting a single patient in a headache clinic who developed persistent localized alopecia at the fremanezumab injection site on the lower extremity. The authors reviewed the clinical presentation, medication history, and existing literature on CGRP inhibitor-associated alopecia to propose a mechanism.
Who was studied
Single adult male patient using fremanezumab for migraine prevention
What this study cannot tell us
As a single case report, this cannot establish causation — the alopecia could be coincidental. No biopsy was described to confirm the proposed immune privilege mechanism. The rarity of injection site-specific alopecia makes it difficult to determine incidence rates or risk factors.
How to read the evidence
This is a single case report — the lowest level of clinical evidence. While it documents an interesting and plausible adverse event with a proposed mechanism, it cannot establish incidence, risk factors, or definitive causation.
When this study was published
Published in 2024, this case report is part of the ongoing post-marketing surveillance of CGRP inhibitors, which have been widely prescribed since 2018. The accumulating alopecia signal is still being characterized.
The bigger picture
CGRP inhibitors represent one of the biggest advances in migraine treatment in decades, but post-marketing surveillance is revealing side effects not captured in clinical trials. The growing pattern of alopecia reports — now including injection site-specific cases — suggests CGRP plays an underappreciated role in hair biology. This has implications not just for migraine treatment counseling but also for understanding CGRP's broader biological functions beyond pain signaling.
Questions still open
- How common is alopecia with CGRP inhibitors in real-world use compared to what clinical trials reported?
- Does the hair loss reverse if the CGRP inhibitor is discontinued, or is follicle damage permanent?
- Could oral CGRP antagonists (like rimegepant or atogepant) carry lower alopecia risk since they don't involve local injection?
Common questions
Can CGRP migraine drugs cause hair loss?
What is CGRP's role in hair growth?
Read the original research
Fremanezumab-associated injection site alopecia.
BMJ case reports, 17(8)
Citation
Esguerra, Mark; Engel, Emily Rubenstein. (2024). Fremanezumab-associated injection site alopecia.. BMJ case reports, 17(8). https://doi.org/10.1136/bcr-2024-260741