Mutation in which collagen is present in epidermolysis bullosa ?
Ans. is 'd' i.e., VII Molecular pathology of EB Normal basement membrane is between epidermal basal layer and dermis. This basement membrane (basal lamina) is attached to basal cells hemidesmosomes with the help of keratin containing intermediate filaments and is attached to dermis (dermal papillary layer) with the help of type VII collegen containing fibrils. Any defect in this anchoring complex leads to separation of skin; the site of separation depends on the type of defect EB simplex --> Mutation in gene coding for keratin 5 & 14 (major keratin of BMZ) and separation will be epidermal. EB junctional --> Mutation in Lantinin a-3 (LAM a-3), LAM [I-3, LAM 7-2 genes. As laminin is pa of basement membrane the separation will be at dermo-epidermal junction (DEJ). EB dystrophicans --> Mutation in collagen VII-Al gene. As collagen VII containing fibrils join BM to dermal papilla, separation will be in the dermis. Any of the above defect results in defective cohesiveness which leads to vulnerability to trauma and blisters formation. As the disease is inherited, Family history may be positive.
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