Epidermolysis Bullosa Disorder Epidermolysis Bullosa, abbreviated as EB, is the term used to describe a genetically-determined skin disorder. EB is characterized by dissolution of the different layers that make up the normal skin. Because of this the different layers of skin do not adhere properly which causes blisters.This disruption takes place in the interface of epidermis and dermis; the basement membrane zone. The strength of this zone and the proper anchoring of both layers into each other is provided by links between cell adhesion molecules and extracelluar matrix proteins. The absence of a particular adhesion molecule caused by genetic mutation leads to a certain extent to the loss of anchoring. The different forms of EB are divided into three groups depending on the level where the disruption and blistering takes place (in the basal cells just above the basement membrane, right through the basement membrane or the layer just below it); EB simplex, junctional EB and dystrophic EB (see relevant sections in this chapter). In healthy people blisters only occur when there is severe friction on the skin, for example, on the foot during a long walk. EB patients can develop blisters by simply wearing clothes and making very ordinary movements. The blisters do heal but only through intensive care. When blisters burst or when they are punctured, large open wounds are sometimes the result and there is a constant danger of infection. The wounds should be dressed very carefully to prevent new blisters due to sliding or removal of the bandage. In addition, there is a constant fear for the patient and carers of healing wounds to open again and the development of new wounds. In the milder forms of EB blistering only occurs on hands and feet. Then, there are problems with, for example, walking and/or operating a keyboard. Apart from that these patients have a normal skin. Besides the skin lesions present, other layers of epithelium can be affected as well. This concerns especially the mucous membrane of the oral cavity, the pharynx and the oesophagus. But lesions can also occur in the dental area, around the anus and in the urinary tract. Disorders in the gastrointestinal tract usually effect the nutritional status which can cause a serious delay in growth. Most forms of EB leave scars. This can lead to permanent invalidity, for example fusion of fingers or toes which frustrates all sorts of activities and the occurrence of mobility problems. One's appearance can be seriously damaged too which results in psychosocial problems. This is especially the case with children and adolescents. Aetiology As a result of thorough scientific research the cause of the various forms of EB has become more clear in recent years. All types of EB are hereditary and have their own inheritance pattern (this is the way in which the disorder is passed on to the next generation). A distinction can be made between the dominant inheritable types and recessive types of inheritance (see diagram inheritance). Dominant inheritable type A dominant form of inheritance means that one of the parents is an EB-sufferer. The chance that the disease is passed on to the next generation is 50% for each child. The child has therefore also a 50% chance to be entirely healthy. Recessive inheritable type In a recessive form of inheritance both parents are healthy, but a carrier of a (recessive) EB-gen. These couples are often not aware that they are a carrier until a child with EB is born. When two carriers join each child has a 25% chance to have the disorder. Besides, there will be a 50% chance that children will be born who are carrying the gen but are healthy otherwise. Finally, there is a 25% chance of a normal child who will not pass on the damaging gen to the next generation. Thousands of people are, without knowing, carrier of a serious type of EB. When they have a partner who is not a carrier of the EB-gen they do not run a risk of getting a child with EB. For couples who know they are both carriers it is possible to find out during the pregnancy whether the child has EB or not (prenatal diagnosis).
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