Psoriasis (1998)

Psoriasis is a common inherited skin disorder. Approximately 2% of the United States population is affected, with 25% to 45% of individuals developing their first clinical signs before 16 years of age. Thus, it is of great importance for all pediatric clinicians to be familiar with this papulosquamous skin disorder.Classic lesions of psoriasis consist of round, erythematous, well-marginated plaques covered by a grayish or silvery white scale. The scale is generally attached at the center rather than at the periphery, and its removal results in fine punctate bleeding. This is called the Auspitz sign and is highly characteristic but not diagnostic of psoriasis. Common sites of involvement are the scalp, elbows, knees, and gluteal crease, resulting in “gluteal pinking.” The amount of body surface area involved varies from trivial to widespread. Nail pitting, when present, is a helpful diagnostic clue. Although psoriasis usually is considered a pruritic disorder, itching can be quite variable. Involvement of the diaper area is quite common in infants and toddlers. Initially,lesions often look like candidal diaper dermatitis with a bright red rash involving the creases. In psoriasis, the rash can spread to the abdomen and legs. The clinician should include psoriasis in the differential diagnosis of any extensive or treatment-resistant diaper rash.A variant of psoriasis called guttate psoriasis (“droplet-like”) may be the first manifestation in children. The lesions are 2 mm to 1 cm in diameter and generally are distributed symmetrically over the trunk and proximal aspects of the extremities. Two thirds of patients who present with guttate psoriasis have a history of an upper respiratory tract infection or streptococcal disease 1 to 3 weeks prior to the onset of rash. Throat or perianal cultures should be obtained in children who have guttate psoriasis. A particularly helpful finding in psoriasis is the Koebner phenomenon, which is when lesions appear at sites of local injury, such as a cut or scrape. The Koebner phenomenon, like the Auspitz sign, is not pathognomonic for psoriasis, but its presence is useful in establishing the diagnosis.The susceptibility to develop psoriasis is inherited, but the exact pattern of inheritance is more complex than simple mendelian genetics. Psoriasis has a strong association with the human leukocyte antigen locus. Recent studies have identified two subtypes of the plaque type, nonpustular form of psoriasis. Although the clinical lesions are indistinguishable, the inheritance is quite different. Type I has an age of onset younger than 40 years and is much more likely to affect a first-degree relative than in type II disease in which the onset is after age 40. Inheritance of psoriasis in children is highest in those who have type I psoriasis and demonstrate the B13 and A2 haplotype in addition to Cw6.Yet-to-be-discovered information about specific T-cell subsets and a variety of cytokines may yield the key to more effective therapy for this chronic disease. Of particular importance in childhood is the role of bacterial superantigens in the development of guttate psoriasis.The treatment of psoriasis is challenging, particularly in children,because therapeutic options are limited. For mild-to-moderate disease,emollients (moisturizers) and topical corticosteroids are often sufficient. Bland emollients, such as petroleum jelly, are inexpensive and easy to use. They alone may improve psoriasis by 40%. Low-to-medium potency topical corticosteroids may be insufficient for control, necessitating the use of potent agents, although they carry a significant risk for tachyphylaxis and local atrophy. They must be used carefully, ideally on an intermittent basis and with close clinical monitoring.Tar and anthralin are age-old agents that may be very helpful in childhood psoriasis. Unfortunately, their odor and mess can reduce compliance significantly.An important new topical agent is calcipotriene, a vitamin D analog. Available in the United States for the past 3 years, it has provided an excellent alternative to topical corticosteroids. Although it has not yet been approved by the United States Food and Drug Administration for use in children, early reports from Europe suggest that it is safe if used on a limited surface area with monitoring of calcium metabolism.Other treatment modalities available for patients who have severe or resistant disease include phototherapy, immunotherapy, and retinoids. Methotrexate at a dose of 0.2 to 0.4 mg/kg once a week for 31.2 to 46.4 weeks resulted in a post-therapy disease-free state of 14.4 to 16.8 weeks in children. Cyclosporin can clear severe adult psoriasis and psoriatic arthritis, but its safety and utility in children has yet to be determined.Childhood psoriasis can cause serious problems with peer relationships and have a significant financial impact on the family. Pediatricians and dermatologists often can control this chronic disease with family education, counseling, and a willingness to explore therapy with a combination of agents.