The other 40% of cases do not show any sunburn reaction. In these individuals, this sunburn reaction can happen in the first weeks of life and is often blamed on neglect or labelled wrongly as cellulitis or impetigo. In about 60% of cases, the first signs are extreme sensitivity to sunlight, which takes many days or weeks to resolve. There are many reviews of the clinical features of XP. Anecdotally, the incidence in North Africa and the Middle East, where there is a high level of consanguinity, is substantially higher. A more recent survey in Western Europe suggests approximately 2.3 per million live births. Estimates made in the 1970's suggested an incidence in the USA of 1 in 250, 000 and in Japan of 1 in 20, 000. Consistent with autosomal recessive inheritance, males and females are similarly affected.
XP has been found in all continents and across all racial groups. Thus, the complete De Sanctis-Cacchione syndrome is present in only very few cases, but several patients have one or more neurological features.
The latter term is currently rarely used as it is evident that there is a wide range of neurological abnormalities of varying severity and varying age of onset.
#XERODERMA PIGMENTOSUM PDF SKIN#
Historically, the disorder was classified originally as "classical XP" (skin abnormalities only) and the De-Sanctis-Cacchione syndrome with skin abnormalities and extreme neurological degeneration. In a minority of cases there are neurological abnormalities of varying severity. About 60% of affected individuals show an exaggerated and prolonged sunburn response. Xeroderma pigmentosum (literally dry pigmented skin), is defined by extreme sensitivity to sunlight, resulting in sunburn, pigment changes in the skin and a greatly elevated incidence of skin cancers. Xeroderma pigmentosum (XP) Orpha 910 Definition In patients with neurological problems, these are progressive, leading to disabilities and a shortened lifespan. In the absence of neurological problems and with lifetime protection against sunlight, the prognosis is good. Although there is no cure for XP, the skin effects can be minimised by rigorous protection from sunlight and early removal of pre-cancerous lesions. Antenatal diagnosis can be performed by measuring DNA repair or by mutation analysis in CVS cells or in amniocytes. These features distinguish XP from other photodermatoses such as solar urticaria and polymorphic light eruption, Cockayne Syndrome (no pigmentation changes, different repair defect) and other lentiginoses such as Peutz-Jeghers syndrome, Leopard syndrome and Carney complex (pigmentation not sun-associated), which are inherited in an autosomal dominant fashion. The clinical diagnosis is confirmed by cellular tests for defective DNA repair. Diagnosis is made clinically by the presence, from birth, of an acute and prolonged sunburn response at all exposed sites, unusually early lentiginosis in sun-exposed areas or onset of skin cancers at a young age.
There is wide variability in clinical features both between and within XP groups. The eighth (XPV or DNA polymerase η) is required to replicate DNA containing unrepaired damage. Seven of the gene products (XPA through G) are required to remove UV damage from the DNA. The products of these genes are involved in the repair of ultraviolet (UV)-induced damage in DNA. There are eight XP complementation groups, corresponding to eight genes, which, if defective, can result in XP. A minority of patients show progressive neurological abnormalities. This is followed by areas of increased or decreased pigmentation, skin aging and multiple skin cancers, if the individuals are not protected from sunlight. The first features are either extreme sensitivity to sunlight, triggering severe sunburn, or, in patients who do not show this sun-sensitivity, abnormal lentiginosis (freckle-like pigmentation due to increased numbers of melanocytes) on sun-exposed areas. Estimated incidences vary from 1 in 20, 000 in Japan to 1 in 250, 000 in the USA, and approximately 2.3 per million live births in Western Europe. It is a rare autosomal recessive disorder and has been found in all continents and racial groups. Xeroderma pigmentosum (XP) is defined by extreme sensitivity to sunlight, resulting in sunburn, pigment changes in the skin and a greatly elevated incidence of skin cancers.
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