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Diagnosis | Epitheliogenesis imperfecta: a hereditary cutaneous disorder of cattle
Epitheliogenesis imperfecta (EI) is a rare hereditary disorder. In cattle, EI is characterized by extensive epithelial defects of skin and mucosa that vary in size and location. Most often, these lesions consist of irregular and discontinuous patches of hair and skin usually on the distal extremities, and patches of missing mucosa in the oral cavity and on the tongue. EI has been reported in cattle18, including Angus3, Ayrshire4, Holstein-Friesian5, Jersey6,7, Shorthorn3, and Sahiwal8 breeds. EI has also been reported in a buffalo9, cats10, a cougar11, a dog12, horses 1317, and sheep1820.
Most reports of EI have only documented its occurrence, and consequently its pathogenesis was until recently poorly understood. Frey et al.21 found that cultured fibroblasts from a calf with EI produced less type-I collagen and a higher percentage of type-III collagen than fibroblasts from normal cattle. In addition, the cultured cells showed decreased synthesis of lipids, especially glycerides and cholesterol21.
Leito et al.15 necropsied two American Saddlebred fillies diagnosed with EI and found the morphological and ultrastructural defects observed in the EI-affected foals were similar to those observed in human newborns stricken with the Herlitz variant of junctional epidermolysis bullosa (JEB). The Herlitz variant of JEB is caused by a defect in one of the subunits of laminin-5, a noncollagenous protein found in the skins basement membrane. Because of the close similarity of lesions in the human and equine diseases, Leito et al.15
suggested that EI may be caused by a defect in laminin-5. Spirito et al.22 showed that EI
in Belgian horses, which is characterized by blistering of the skin and oral epithelium and exungulation (loss of the hoof), is caused by the failure to express the laminin-2 chain of laminin-5. They designated Lamc2 as the candidate gene and showed that EI in the Belgian horse genetically corresponds to the Herlitz variant of JEB in humans22.
Epidermolysis bullosa in humans is a group of skin disorders that presents as blistering of the skin in varying degrees of severity. Most cases are inherited, but rare cases may be acquired. There are three main types: simplex, junctional, and dystrophic. The dermal-epidermal junction of the newborn skin is a vital area of...