Loose anagen syndrome: This condition, whose onset is usually before 8 years of age, is characterized by short, very slow-growing hair. The hair pull yields anagen hairs, which under the microscope have a distinctive appearance marked by a rolled-up proximal tip.
Short anagen syndrome: The hallmarks here are decreased hair density, increased shedding, and an inability to grow hair long. On the hair pull, affected patients have an increased number of telogen hairs. The telogen hairs, which are newly regrowing in response to the truncated anagen cycle, will have a tapered tip at the distal end.
Scalp biopsy is of variable utility in diagnosing the cause of diffuse hair loss in young patients. It can be used to make the diagnosis of certain conditions, including acute alopecia areata, trichotillomania, connective tissue disease, infection, tumor, and scarring disorders. However, scalp biopsy can’t be used to make a definitive diagnosis of telogen effluvium, androgenetic alopecia, or long-standing alopecia areata – it can only be suggestive.
Pathologic standards dictate that the scalp biopsy should always be 4 mm. Normal white adults have roughly 36 follicles per 4-mm biopsy. African American adults have about 22. While no standard numbers have been established for children, the number of follicles per biopsy is higher than in adults because of the child’s smaller head size. After all, the number of follicles present at birth is what an individual will carry throughout life, Dr. Olsen explained.
It’s important that patients and parents understand the need for patience regarding hair regrowth, which takes 6-12 months after the cause of alopecia has been identified and eliminated. That means, for example, that in a patient with thyroid disease the clock for regrowth starts ticking not at the time treatment begins, but when the patient becomes euthyroid.
Dr. Olsen reported serving as a consultant to Canfield Scientific and Allergan.