Abstract
Alopecia areata (AA) is the second most common cause of hair loss. It is crucial for the clinician to differentiate AA from other types of hair loss as it differs in prognosis and treatment. The diagnosis of AA can be made clinically; however, there are many nuances making an exact diagnosis challenging. This paper describes the differential diagnoses of both scarring and non-scarring hair loss that may mimic AA. It also highlights the diagnostic tests and pertinent findings that help distinguish AA from other types of hair loss.
Financial & competing interests disclosure
The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.
No writing assistance was utilized in the production of this manuscript.
Key issues
• Alopecia areata (AA) is the second most common cause of hair loss. There are numerous treatment regimens; however, none are curative nor preventative.
• AA can present heterogeneously, ranging from one or more well-circumscribed, discrete, smooth, scarless, hairless patches to very rapid and dramatic hair loss.
• AA most commonly presents on the occipital scalp.
• AA should be considered in the presence of other autoimmune diseases, as it is an immune-mediated disease of the hair follicle.
• AA is a non-scarring form of hair loss that can clinically mimic other types of scarring and non-scarring alopecias.
• The wash test, pull test and most importantly dermoscopy are non-invasive tests that help to distinguish AA from other types of alopecia.
• In addition to diagnosis, dermoscopy can evaluate disease progression and response to treatment.
• Dermatoscopic patterns of AA include yellow dots, micro-exclamation mark hairs, broken hairs, cadaverized hairs or black dots. Loss of follicular openings indicates scarring alopecia which rules out a diagnosis of AA.