ORLANDO — Pediatric skin conditions often pose diagnostic challenges because many cutaneous disorders have similar clinical features.
Annular lesions of granuloma annulare may be mistaken for tinea corporis; follicular papules of keratosis pilaris may be confused with follicular eczema; and nail psoriasis may be misdiagnosed as onychomycosis.
At a meeting sponsored by the American Academy of Pediatrics, Albert C. Yan, M.D., director of pediatric dermatology at the Children's Hospital of Philadelphia, provided some helpful diagnostic tips for distinguishing some of these potentially puzzling skin problems.
The Hair Collar Sign
A boy is born with an area of localized, circular alopecia covered by a glossy membrane. The area is surrounded by a collection of dark, terminal hairs. Palpation reveals that a lump is present.
Occasionally mistaken for fetal scalp monitor trauma, neonatal herpes simplex infection, or a nevus sebaceus of Jadassohn, this characteristic pattern—a collar of coarse hair surrounding an area of membranous aplasia cutis congenita—can be a marker for cranial dysraphism, a developmental defect of the skull potentially associated with structural neurologic defects. The scalp defect may represent only the tip of the iceberg, Dr. Yan noted, since underlying bony defects or ectopic brain tissue may be present.
In such cases, magnetic resonance imaging is essential to rule out underlying abnormalities, including atretic encephaloceles or heterotopic brain tissue.
Pilomatricoma
A 15-month-old girl presented with a bump on her cheek—a firm, bluish, cystic papule that moved back and forth under pressure. When one end of the lesion was palpated, the other end would pop up, a phenomenon also known as a “teeter-totter sign.”
Although these lesions may resemble dermoid cysts or epidermal inclusion cysts, the diagnosis in this case was pilomatricoma, distinguished by its bluish color and the presence of the teeter-totter sign. The lesions most often occur on the head or neck, although other areas occasionally are affected. Pilomatricomas generally are solitary, benign, frequently calcified, and arise from hair follicles. In some cases, the lesions resolve spontaneously, but more often, they persist and grow, and surgical intervention is recommended. Pilomatricomas may rupture, which can cause inflammation and scarring. Although pilomatricomas generally are isolated findings, they may be associated with systemic disorders such as Gardner's syndrome, myotonic dystrophy, and sarcoidosis.
Annular Urticaria/Urticaria Multiforme
A 3-year-old girl presented with red, swollen, annular plaques on her skin, and had swollen hands and feet. She had been otherwise healthy and was taking no medications. The condition arose suddenly; the parents noticed the rings and swelling one morning when picking up the child from her bed. On closer inspection, the rings were red and blanchable, with clear white centers. Some were imperfect circles.
The diagnosis is annular urticaria. “These types of cases are frequently referred for suspected erythema multiforme,” Dr. Yan noted. “Lesions of annular urticaria are evanescent; the lesions fade and move, and the lesions can form imperfect circles with clear centers. The lesions may disappear within 24 hours, only to show up elsewhere,” he said. By contrast, erythema multiforme appears as fixed target, or “bull's-eye,” lesions with dusky centers and is associated with mucous membrane ulcers.
The two conditions are treated quite differently, Dr. Yan emphasized. Annular urticaria responds to combinations of antihistamines or occasionally steroids; erythema multiforme requires a detailed history to determine underlying causes, removal or treatment of those causes, and consideration of steroid therapy if indicated. Dr. Yan often refers to annular urticaria as “urticaria multiforme” because these cases are so regularly mistaken.