Pediatric psoriasis: Presentation in childhood linked to genetics

May 1, 2008

Psoriasis has a stronger genetic component when it presents in childhood than when it presents in adulthood. In children, scalp involvement is very common if they present with psoriasis. In addition, presentation in childhood is correlated with a greater tendency for more severe psoriasis over one's lifetime.

Key Points

Toronto - When psoriasis presents in children, the genetic component is stronger than when the disease has its onset in adulthood, according to the program director for the dermatology residency program at the University of Toronto.

Speaking at a symposium in pediatric dermatology, Scott Walsh, M.D., Ph.D., assistant professor of dermatology at Sunnybrook Health Sciences Centre, Toronto, discussed the pathology of psoriasis in children and possible therapies for psoriasis in children.

In adults, as in children, psoriasis is a chronic, T-cell-mediated immune skin disease that is characterized by inflammation, keratinocyte proliferation and vascular proliferation.

In particular, there is high concordance of the risk allele HLA-CW6 with early-onset psoriasis and strong family history.

"If you are very unlucky and have two parents and a sibling who have psoriasis, studies suggest that your chance of getting the illness is as high as 83 percent," Dr. Walsh tells Dermatology Times.

"If you have one sibling who has psoriasis, then the risk is significantly less, at 24 percent," he says.

The risk of developing psoriasis is 28 percent for patients with one parent with psoriasis, 41 percent for patients with a sibling and one parent who have psoriasis, and 65 percent for those with two parents who have psoriasis.

The presentation of psoriasis in children can differ from that in adults, Dr. Walsh says.

"Scalp involvement is also very common in children," he says. "Children have a greater tendency for having more severe disease over their lifetimes."

In close to one-third of all pediatric cases, guttate flares occur. Small plaques appearing after an upper respiratory tract infection or streptococcal infection, originating from the throat or perianal area, characterize guttate flares.

The presence of psoriasis in children does not guarantee chronicity of the disease; however, the presence of psoriasiform napkin dermatitis can lead to chronic plaque psoriasis in a minority of cases.

Similarly, roughly one out of four children who have guttate psoriasis can go on to develop chronic plaque psoriasis.

Factors that can either trigger or exacerbate psoriasis include trauma, infection, group A beta-hemolytic streptococci, stress and certain medications. As a T-cell mediated genetic disease, psoriasis can be triggered by environmental stimuli.

When infants have diaper dermatitis that appears unresponsive to standard treatments, clinicians should consider psoriasis.

When psoriasis is present in an infant, the margins are sharply demarcated, and it involves groin folds.

When children develop psoriasis, in the majority of cases (70 percent), the psoriasis takes the form of chronic plaque psoriasis. There are well-defined classic plaques in children who have psoriasis, and it affects sites such as extremities and the trunk. There is also facial involvement in up to nearly half of cases.

Children should be encouraged to not pick at their scales to minimize trauma to the skin, to avoid immune-boosting medications and to use moisturizers on the skin that have a Vaseline base.

There are fewer therapeutic choices for managing psoriasis in children compared to choices available to treat psoriasis in adults. Still, topical corticosteroids can be safely administered.

The formulation should be appropriate to the body site, with cream being more effective for skin folds, ointment being more effective for the body, and lotion being more effective on the scalp.

The appropriate type of steroid therapy varies depending on the site that is involved in the presentation. Hydrocortisone is suggested for the face and folds, bethamethasone valerate (or equivalent strength) is recommended for the body and scalp, and fluocinonide is suggested for palms and soles.

"Absorption is not such a serious issue if the steroids are used appropriately on different body sites," Dr. Walsh says.

Systemic corticosteroids should be avoided in children with psoriasis, when possible. If systemic therapy is required because patients have not responded to other treatments, off-label cyclosporine is effective and is often well-tolerated, he says.

While not indicated for psoriasis, calcineurin inhibitors such as tacrolimus and pimecrolimus have shown efficacy in the treatment of psoriasis. Dr. Walsh suggests that the off-label use of calcineurin inhibitors be limited to the face and folds, where efficacy has been sufficiently supported with clinical data.

Tar derivatives are effective in treating thick body plaques, and topical vitamin D can be used on the body or scalp.

Phototherapy using narrowband ultraviolet-B is another treatment modality available for children with psoriasis. Therapy can be administered at a frequency of two to three times per week.

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