Genetic skin disease

There are several genetic skin diseases with known defects in the lipid metabolism. Atopic dermatitis, lamellar ichthyosis, and psoriasis have been the most widely studied with respect to epidermal barrier function and alterations in the lipid profile. Deviations in the lipid profile have been linked with an impaired stratum corneum barrier function. Atopic dermatitis is characterized by inflammatory, dry and easily irritable skin, and overall reduced ceramide levels in the stratum corneum [58-60]. In particular a significant decrease in the ceramide 1 level is observed, whereas the levels of oleate that is esterified to ceramide 1 are elevated [59]. Both aberrations may be responsible for the reduced order of the lamellar phases as observed with freeze fracture electron microscopy [61]. It has further been established that, in comparison to healthy stratum corneum, the fraction of lipids forming a hexagonal packing is increased [61]. A recent study reveals that the level of free fatty acids... 

Skin Epithelial Burns Ulcers Genetic skin diseases... 

VassarR, Coulranbe PA, Degenstein L, Albers K, Fuchs E (1991) Mutant keratin expression in transgcmic mice causes marked almormalities resembling a hitman genetic skin disease. Cell 64 (2) 365-380... 

There are many reviews on constitutes a mouse model for human diseases (5-7), as well as models for specific diseases (8-22). It is beyond the scope of this chapter to discuss the pros and cons of each of these potential models, especially since a recent scan of the public literature and databases revealed over 1200 genetically engineered and spontaneous mouse mutations that have skin diseases that potentially serve as models for specific human diseases. Information on these are and where to find them is discussed below. Further, this chapter will not describe the usefulness of the mouse to study wound healing, and the reader is referred to other reviews on such (23, 24). 

The twins were referred subsequently to a metabolic specialist because of the suspicion of an inborn error of metabolism. Biochemical testing revealed each had a hyperchloremic (increased blood chloride concentration) metabolic acidosis that was more profound in Elizabeth. Serum levels of glucose and liver transaminases were normal. Urinary organic acids revealed modestly increased concentrations of lactate and ketone bodies. Blood samples and fibroblasts from skin biopsies from both girls were sent to an established diagnostic laboratory for genetic mitochondrial diseases. Tests of respiratory chain complex enzymatic activities were normal. 

Eczema is caused by environmental influences affecting genetically predisposed individuals [146(111), 147(111)]. It is the most frequent inflammatory skin disease in childhood. Prevalence estimates for eczema ranged between 1.1 and 3.1% in the early literature, however, in newer studies these figures reach 25% based upon questionnaires, and 12.9% based upon dermatological examinations. There is evidence that the IgE-associated subgroup of eczema, atopic eczema, has increased in frequency over the past decades. 

There are several genetically determined diseases such as xeroderma pigmentosum (XP), Fanconi s anemia. Bloom s syndrome, ataxiatelangiectasia and porokeratosis Mibelli in which individuals have an increased if not an invariable incidence of cancer (291. These diseases are associated with DNA repair defects, thought to be the cause of the cancer sensitivity (291. In the case of a person with XP, the oversensitivity of the skin to ultraviolet light is inherited and the condition leads to skin cancer. 

A number of rare genetic diseases involve collagen abnormalities, including Marfan s syndrome and the Ehlers-Danlos syndromes, which result in hyperextensible joints and skin. The formation of atheroselerotie plaques, which cause arterial blockages in advanced stages, is due in part to the abnormal formation of collagenous structures in blood vessels. 

Psoriasis is a T-lymphocyte-mediated inflammatory disease that results from a complex interplay between multiple genetic factors and environmental influences. Genetic predisposition coupled with some precipitating factor triggers an abnormal immune response, resulting in the initial psoriatic skin lesions. Keratinocyte proliferation is central to the clinical presentation of psoriasis. 

Defects have been found in these mechanisms that cause various human diseases. For example, patients with the genetic disease xeroderma pigmentosum are especially sensitive to ultraviolet light and develop skin cancer. Skin fibroblasts cultured from these patients have been shown to be defective in DNA repair. 

The development of nevirapine-induced disease is clearly immune-mediated as upon re-challenge with nevirapine the rash developed faster in previously exposed and fully recuperated rats. In addition, memory for skin reactions in response to nevirapine were transferable by splenocytes from treated to naive animals [15]. In summary, nevirapine-induced skin reactions in rat are immune-mediated and dependent on genetic background, including gender. 

The mechanisms of autoimmunity may also entail interaction with MHC structures determined by the HLA alleles. Individuals carrying certain HLA alleles have been shown to be predisposed to certain autoimmune diseases, which may account in part for the genetic variability of autoimmunity. In addition, metabolites of a particular drug may vary between individuals to confound the development of drug-induced autoimmunity. Dendritic cells, such as the Langerhans cells of the skin and B lymphocytes that function to present antigens to Th cells, express class-II... 

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