Disease:Defects in KRT4 are a cause of white sponge nevus of cannon (WSN) [MIM:193900]. WSN is a rare autosomal dominant disorder which predominantly affects non-cornified stratified squamous epithelia. Clinically , it is characterized by the presence of soft , white , and spongy plaques in the oral mucosa. The characteristic histopathologic features are epithelial thickening , parakeratosis , and vacuolization of the suprabasal layer of oral epithelial keratinocytes. Less frequently the mucous membranes of the nose , esophagus , genitalia and rectum are involved. ,miscellaneous:There are two types of cytoskeletal and microfibrillar keratin: I (acidic; 40-55 kDa) and II (neutral to basic; 56-70 kDa) . ,polymorphism:Three alleles of K4 are known: K4A2 (shown here) , K4A1 and K4B. ,similarity:Belongs to the intermediate filament family. ,subunit:Heterotetramer of two type I and two type II keratins. Keratin-4 is generally associated with keratin-13. ,tissue specificity:Detected in the suprabasal layer of the stratified epithelium of the esophagus , exocervix , vagina , mouth and lingual mucosa , and in cells and cell clusters in the mucosa and serous gland ducts of the esophageal submucosa (at protein level) . Expressed widely in the exocervix and esophageal epithelium , with lowest levels detected in the basal cell layer. ,
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