Diagnosing Bald Spots

About 95% of hair loss in childhood is acquired and localized. The big three causes for this circumscribed baldness are:

Tinea Capitus

Ringworm of the scalp is the most common cause of alopecia (hair loss) in children. The fungus Trichophyton tonsurans which infects mostly prepubertal children accounts for more than 90% of cases. A few children are affected by the dog ringworm Microsporum canis which produces a yellow-green fluorescence under the ultraviolet light of a Wood’s lamp. (Trichophyton species do not fluoresce.)

In the noninflammatory stage of T. tonsurans, hair breaks off at scalp level, leaving small, dark hairs in the follicles. This stage is called black-dot ringworm.

In the inflammatory stage, the infection progresses to:

A kerion is a red, boggy nodule with superficial pustules. It is usually accompanied by suboccipital or posterior cervical lymphadenopathy.

A near-epidemic of T. tonsurans infections is in progress in this country. Treatment is oral Griseofulvin (20 mg/kg/day) for eight weeks. No topical preparation is considered effective treatment.

Alopecia Areata

There is usually an abrupt onset of hair loss in one or several round or oval patches.

There are no pruritis, scaling or broken hairs. The cause is unknown and no treatment is necessary as hair regrowth is the rule.

Traumatic Alopecia

External injury to the hair or hair follicle is the third most common cause of acquired circumscribed hair loss in children. The trauma can be chemical or thermal, or the result of traction or friction. Most common are trichotillomania (compulsive pulling out of one’s own hair) and traction alopecia due to certain hair styling and care practices, particularly tight braiding of the hair in African-Americans.

Treatment depends on the cause, e.g., change of hair style or psychiatric treatment of compulsive behaviors.

The following table gives diagnostic clues for the three conditions.

Tinea capitis

History of infected contacts

Scaly scalp with broken hairs in the follicle; may

have keroin

Positive fungal culture

KOH (potassium hydroxide) examination reveals

hyphae and spores on the hair shaft

Alopecia areata

Family history Negative fungal culture

Scalp shows no changes Negative KOH

Nail pitting examination

Traumatic alopecia

History of trauma to hair Scalp excoriations

Hair style harsh to hair Negative fungal culture

Hairs broken off at Negative KOH

differing lengths examination

Perifollicular petechiae

(Panos V. Bald spots: Remember the "big three". Contemporary Pediatrics 1997;14(10):76-91)

COMMENT: All students with undiagnosed hair loss warrant a referral by the school nurse. Primary care physicians can manage the majority of cases, while a dermatologist may be consulted if diagnosis is uncertain. - R.A.