Picture Review: Dermoscopy Distinguishes Hair Disorders

^{All photos courtesy Dr. Antonella Tosti}

Normal Scalp. Normally, hairs are arranged in follicular units, with up to three hair shafts from the same orifice. "You also see single hairs coming out from the scalp," Dr. Tosti said. Most hair disorders feature a high number of single hairs. A normal vascular pattern presents as interfollicular red loops and arborizing red lines.

Psoriasis. Twisted, coiled loops are a sign of scalp psoriasis. Folliculitis decalvans is the only other scalp condition with a similar loop presentation. If you observe white scales, use high-magnification dermoscopy to look at the vessels before diagnosing psoriasis. White scales can also be seen in cicatricial alopecias such as lupus erythematosus and lichen planopilaris. "So you may need to take a biopsy when patient presents with wide, white scales. It's not always psoriasis," Dr. Tosti said.

Alopecia areata. Alopecia areata and androgenetic alopecia each will feature yellow dots that correspond to follicular openings. "How often you see the yellow dots depends on the patients. They are seen often in [whites] and less commonly seen in darker-skinned patients," Dr. Tosti said. Hair diameter variability, a sign of androgenetic alopecia, can help you to distinguish these conditions. More than 20% variability in shaft thickness and an increase in the number of thinner hairs with advanced disease are diagnostic. "My suggestion is always use your dermatoscope when women complain of hair loss," Dr. Tosti said. "It is an easy and quick way to distinguish androgenetic alopecia."

Discoid lupus erythematosus. A follicular red dot pattern is characteristic of this condition on dermoscopy. An atrophic epidermis can be seen in active lesions. The red dots are important to recognize because, if treated, hair can regrow in the affected area. "Make the diagnosis early and treat the patient immediately," Dr. Tosti said. Also, the red dot pattern will help you to distinguish this disorder from other conditions that can cause cicatricial alopecia.

Cicatricial alopecia. A loss of follicular openings is an important clue on dermoscopy that indicates cicatricial alopecias

Traction alopecia. Hair casts are a useful dermoscopy clue for this condition. "You can see them immediately," Dr. Tosti said. "Hair casts are also useful in African Americans if their hairstyle is associated with traction, even if they don't have alopecia. Sometimes they will deny a traction hairstyle."

Tinea capitis. Dermoscopy facilitates this diagnosis. Look for comma-shaped hairs, a very specific sign seen in both ectothrix and endothrix T. capitis infections. "This is something you should look for in children. It's very fast," Dr. Tosti said. The comma hairs will be more numerous in recent infections, she added.
Correct diagnosis is important to guide treatment, Dr. Tosti said. "A patient of mine with Microsporum canis infection was previously treated with steroids for folliculitis decalvans. The patient eventually cleared after antifungal treatment."

Monilethrix. Dermoscopy can help you diagnose this condition very, very fast, Dr. Tosti said. The condition features beading of the hair shafts. The autosomal recessive form of monilethrix will appear much more severe on dermoscopy (J. Invest. Dermatol. 2006;126:1292-6).