Psoriasis

Psoriasis, a common inflammatory skin disorder, has received
attention as a target for new pathogenesis-oriented biologic therapies. In this
article, we review the genetic, clinical, and pathogenic aspects of psoriasis and
discuss their implications for new therapies
Though psoriasis is a common skin disease, its definition by Ferdinand von Hebra as a
distinct entity dates back only to the year 1841, and estimates of its prevalence —
around 2 percent, according to standard textbooks — stem from only a few population-
based studies. Perhaps the most comprehensive field study was performed in the
Faroe Islands, where 2.8 percent of the inhabitants were reported to be affected.
This prevalence rate is higher than that in central Europe, where prevalence is approximately
1.5 percent, according to a more recent analysis.
Ethnic factors also appear to influence
the prevalence of psoriasis, which ranges from no cases in the Samoan population
to 12 percent in Arctic Kasach’ye.
The influence of ethnic factors is particularly
evident when one compares prevalence rates within the United States. The prevalence
among blacks (0.45 to 0.7 percent)
is far lower than that in the remainder of the U.S.
population (1.4 to 4.6 percent)Numerous family studies have provided compelling evidence of a genetic predisposition
to psoriasis, although the inheritance pattern is still unclear.
The illness develops
in as many as half of the siblings of persons with psoriasis when both parents are
affected, but prevalence falls to 16 percent when only one parent has psoriasis and to
8 percent when neither parent is affected.
The concordance rate for monozygotic
twins is around 70 percent, as compared with some 20 percent for dizygotic twins, a
finding that further supports the concept of genetic predisposition.
As many as 71
percent of patients with childhood psoriasis have a positive family history
 People with psoriasis typically have sharply demarcated
chronic erythematous plaques covered by silvery
white scales, which most commonly appear
on the elbows, knees, scalp, umbilicus, and lumbar
area. An inverse type of psoriasis
spares these sites and instead appears in intertriginous
areas, where scaling is minimal.
Eruptive guttate psoriasis, which may be the initial
manifestation of the disease and is often preceded
by streptococcal infection by two to three weeks,
exhibits small, disseminated erythematosquamous
papules and plaques. Psoriatic diaper rash
appears to be the most common type of psoriasis
in children under the age of two years
The Picture: