Pediatric psoriasis shares some but not all features of adult psoriasis. Being familiar with the disease’s impact on children helps dermatologists optimize a growing therapeutic armamentarium, including biologics that were FDA approved in the last year for children with chronic moderate-to-severe plaque psoriasis.
Psoriasis is thought to affect about 2.6 percent of the U.S. population. First outbreaks usually appear between ages 15 and 35; however, about 20,000 children under 10 years of age are diagnosed with the skin disease each year, according to the National Psoriasis Foundation.
That’s probably an underestimate, according Elaine C. Siegfried, M.D., professor of pediatrics and dermatology at Saint Louis University Cardinal Glennon Children's Hospital, in St. Louis.
“I think psoriasis is under-recognized in children. And one of the reasons is that some of the clinical features are different than those of adult psoriasis,” she said.
Psoriasis is easy to diagnose in children who present with classic, sharply circumscribed plaques with silvery scale on the trunk and extremities.
“But many children with psoriasis present with involvement limited to the face and diaper area, or skin lesions that are not as scaly or indurated as those typically seen in adults,” Dr. Siegfried said.
Another challenge with diagnosing pediatric psoriasis is a related condition that some call “psoriasis-eczema overlap,” characterized by ambiguous lesions with features of both psoriasis and eczema. Other descriptive names for the condition are nummular eczema, psoriasiform dermatitis and PsEma.
“Overlap is actually quite common. I think it’s more common than classic psoriasis in children, but there is no clinical, histologic or laboratory biomarker to distinguish it from psoriasis or eczema or establish it as a mix of both” Dr. Siegfried says. “So, it’s a controversial diagnosis.”
The lesions of overlap are well-circumscribed and nummular, but without coarse silvery scale. These children also often have scalp, posterior auricular and palmoplantar involvement, as well as nail pits, ichthyosis vulgaris and atopic comorbidities, she said.
Distinguishing overlap from other forms of eczema is important because it’s relevant to prognosis and treatment—especially biologic treatment when the skin condition is severe, according to the dermatologist. And unlike eczema, which tends to wane with age, pediatric psoriasis has a less predictable course, with or without periods of remission, she said.
“Making a diagnosis of overlap requires a careful exam for all the clues,” she says. “The posterior auricular scale and nail changes in young children and infants can be subtle and are easily overlooked.”
Another psoriasis variant that occurs in children and adults is paradoxic psoriasis, which can be triggered by drugs that are used to treat psoriasis.
“Psoriasis is not just one disease; it’s a phenotype with different subtypes,” Dr. Siegfried says.