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The mother of a 3-year-old boy has brought him to the clinic for you to evaluate thinning of his scalp hair over the past month. She reports that the hair loss is occurring "all over" his scalp and that she has not noticed him scratching his scalp or pulling his hair. He was hospitalized four months ago for a rotavirus infection.
Dr. Kudchadkar is a resident in the department of pediatrics at the Johns Hopkins University School of Medicine, Baltimore.
DR. COHEN, who serves as section editor for Dermatology: What’s your Dx?, is director, Pediatric Dermatology and Cutaneous Laser Center, and associate professor of pediatrics and dermatology at Johns Hopkins University School of Medicine. He is a contributing editor for Contemporary Pediatrics.
The author and section editor have nothing to disclose in regard to affiliations with, or financial interests in, any organization that may havean interest in any part of this article.
On examination, you note that the thinning of the hair is diffuse. His scalp appears healthy, however, without erythema or scaling.
Diagnosis: Telogen effluvium
This form of hair loss affects children and adults and is the most common cause of nonscarring, noninflammatory, diffuse hair loss in children.1 To understand telogen effluvium, it is necessary to understand the normal hair growth cycle.
Life cycle of a hair follicle
An individual hair follicle has a long growth phase, known as anagen, in which the hair grows steadily for two or three years. At any given time, 85% to 95% of all follicles on the scalp are in anagen. This phase is followed by catagen, a transitional phase of approximately three weeks during which the hair follicle degenerates. The last phase of growth is telogen, a resting phase during which the hair remains attached to the upper portion of the hair follicle for three or four months before it is shed.
After telogen, anagen begins again: A new hair grows and pushes out the old shaft of hair. About 100 hairs are shed and replaced by new hairs daily.1-3
An imbalance of phases
Telogen effluvium occurs when a large number of anagen hairs have been prematurely pushed from the growth phase into the resting (telogen) phase.4 Anagen hairs are firmly attached at the root, whereas telogen hairs are loosely attached and therefore fall out easily. A sudden, abnormal change in hair growth dynamics that triggers this switch from anagen to telogen is precipitated by a systemic insult; in a child, such insults include high fever, severe illness, surgery, stress, vitamin deficiency, and certain drugs.1,4 (Other causes in adults include childbirth and crash dieting.) Notably, your patient was hospitalized for rotavirus infection before the hair loss began.
Diagnosis of telogen effluvium can be confirmed early in its course by examining hairs pulled from the scalp and demonstrating an increased percentage (to as high as 50% from a normal 10% to 15%) of telogen hairs1 and by observing their somewhat dry, lusterless appearance.
What is the differential diagnosis?
Alopecia areata This disorder is characterized by the sudden appearance of sharply circumscribed, round or oval patches of hair loss anywhere on the body. As in telogen effluvium, the scalp is smooth, without inflammation, scaling, or broken hairs; patches of hair loss appear, literally, overnight, however, or, sometimes, over a few days.4 Hairs at the border of bald spots sometimes can be easily plucked and have an exclamation-point appearance because the bulb of the hair is swollen at its base.
The cause of alopecia areata is likely immunologic. About 25% of affected children also have pitting or ridging of the finger and toe nails. With or without treatment, all hair grows back within one year in about 95% of patients. About 5% go on to develop alopecia totalis-loss of all hair on the scalp-and some of those patients develop alopecia universalis, complete loss of body hair.1,4
Trauma Traction alopecia occurs when hair is worn in a style such as braids, plaits, and ponytails, which causes a tight pull on hair shafts and results in fracture of the shaft. Hair loss is most prominent along parts in the hair and at the periphery of the scalp.1,3