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“Black dot” alopecia areata

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By Warren R. Heymann, MD
April 16, 2016

This week I had a 35 year old man present with a one month history of a round patch of alopecia. He was told by his PMD that he had tinea and was started on oral terbinafine (which he had been on for 5 days when he first came to me). I saw the perfectly round patch of alopecia with exclamation mark hairs and of course diagnosed alopecia areata. I also noted some very short dark hairs, however, and took out my dermatoscope and saw “black dots”. Could this be tinea capitis mimicking alopecia areata? I took a culture, told him that while I felt it was probably alopecia areata, he should continue the medication until the culture results are available. Presumably, the results would be negative, and I would then treat him for AA in the standard manner.

I did some homework today and came across the following article:

Clin Exp Dermatol. 2012 Aug;37(6):615-9. doi: 10.1111/j.1365-2230.2012.04401.x. Epub 2012 Jun 8.’Black dots‘ seen under trichoscopy are not specific for alopecia areata. Kowalska-Oledzka E1, Slowinska M, Rakowska A, Czuwara J, Sicinska J, Olszewska M, Rudnicka L.

Boy oh boy, did I miss the boat!

According to the authors:

“A black dot is defined as a hair in which the upper part of the hair root remains adherent to the hair-follicle ostium, giving the macroscopic appearance of a macrocomedo. We believe that a number of factors may induce formation of black dots, including perifollicular lymphocyte infiltration in the course of an autoimmunologically mediated inflammatory process in AA, a mixed neutrophil-lymphocyte inflammatory infiltration in DCS, cytotoxic and antiproliferating effects of chemotherapeutic agents, and nonspecific factors such as mechanical injury in healthy people.”

I will cut myself a little slack because they used a video dermatoscope and state:

“In the past, probably because of limitations of diagnostic procedures, black dots were rarely recognized in conditions other than AA. Even dermoscopy with a hand-held device (giving a magnification of 7–10) does not allow differentiation of black dots from dystrophic hair or broken hair in patients with trichotillomania or mycotic infection.”

I just called the patient back to tell him to stop the terbinafine, and try topical clobetasol. If, on the remote chance, the culture is positive, we can always restart it. My guess is that there will be no need to do so.

I have always equated alopecia with black dots as being Trichophyton tonsurans until proven otherwise. Unfortunately, I learned that rule well before dermoscopy and trichoscopy became in vogue.

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