I came across this interesting research article published in the JAAD, September 2013, 69(3) by Pai-Shan Cheng, MD, and Feng-Jie Lai, MD, PhD. It discusses a new sign for the rapid microscopic diagnosis of hair changes and hair loss with or without pustualr lesions developing with EGFR inhibitors (Gefitinib or Erlotinib); such drugs have been widely used nowadays in treatment of many cancers.

Normal microscopic examination in plucked hair usually reveals a large caliber of hair root with a pigmented bulb and firmly attached inner and outer root sheaths. In hair changes associated with EGFR inhibitors the authors reported degeneration of the distal part of root sheaths and a distal split of the remaining proximal part, giving an ‘‘arrow’’ appearance microscopically. This arrow sign can be found not only in patents reporting hair or scalp change, but also in those patients having no detectable hair loss or scalp change. Scalp skin biopsies showed: an atrophic outer root sheath with more obvious change in the distal third part. There was a cleft like area over the outer root sheath coinciding with the above mentioned split. The authors recommended at least 5 hairs should be obtained from a single patient for a proper diagnosis.

The authors recommend this sign to be used for rapid microscopic diagnosis of such hair changes in such patients and to use it to exclude fungal infection as these hair changes may mimic tinea capitis.

“Arrow” sign: A rapid microscopic diagnosis of hair change associated with epidermal growth factor receptor inhibitors
[center][b]Journal of the American Academy of Dermatology[/b]
[url="http://www.jaad.org/issues?issue_key=S0190-9622(13)X0008-8"]Volume 69, Issue 3[/url][u], Pages 489-492, September 2013[/u][/center]