A Mechanobullous Disease with Sub-basilar Separation in Brangus Calves

Autor: K. G. Thompson, R. A. Crandell, W. W. Rugeley, R. J. Sutherland
Rok vydání: 1985
Předmět:
Zdroj: Veterinary Pathology. 22:283-285
ISSN: 1544-2217
0300-9858
DOI: 10.1177/030098588502200311
Popis: Mechanobullous diseases are a heterogeneous group of hereditary blistering disorders which have generally been classified under the term ‘epidermolysis b~llosa.’*~~-* The latter term, however, is considered inappropriate since not all forms of the disease are characterized by lysis of the epidermis.’ Several different forms of mechanobullous disease are recognized in man and are grouped according to their clinical manifestations, mode of inheritance, and site of bulla formation.2,7,8 In domestic animals, similar diseases have been reported in Angus calve^,^ Suffolk and South Dorset Down sheep,’ and collie dogs.’ We report the occurrence of a mechanobullous disease in Brangus calves that resembled the recessively inherited form of dermolytic bullous dermatosis as described in man. Three Brangus calves in Texas developed skin loss on their distal limbs within the first few days of life. One calfwas killed at 24 hours, and another developed severe lesions on all four limbs and died at two weeks of age. Neither calf was available for necropsy. The third affected calf survived for four weeks but did not improve and was submitted live to the Texas Veterinary Medical Diagnostic Laboratory. The relationship between affected calves and their parents is shown in fig. 1. Affected calves were sired by two different bulls (B and C), but both bulls had the same sire (A). All cows which produced affected offspring were also sired by bull A. Grossly, there was extensive skin ulceration on the distal limbs and over pressure points, including carpal and tarsal joints. Ulcerated areas were hemorrhagic and had firmly adherent crusts of coagulated exudate (fig. 2). The hooves had sloughed from all four digits on the hind limbs and from one digit on each forelimb, exposing the bright red corium (fig. 2). Most of the nasolabial mucosa was hanging as a flap from the bright red and hemorrhagic submucosa of the muzzle. Several ulcers up to 2 cm in diameter were found on the tongue and hard palate. Histologically, in ulcerated areas of skin the superficial dermis contained degenerate collagen, proliferating capillaries and fibroblasts, and was partly covered by a layer of coagulated proteinaceous exudate that contained many neutrophils, occasional bacterial colonies, and fragments of plant material. Ducts of apocrine glands were often markedly dilated. In the intact epidermis there were various degrees of acanthosis, sometimes associated with rete ridge formation, and focal hyperkeratosis. In many areas there were distinct clefts beneath the basal layer of the epidermis; this created bullae which contained pale-staining proteinaceous fluid and small numbers of inflammatory cells-including neutrophils, eosinophils, and macrophages (fig. 3 ) . In periodic acid-Schiffstained sections it was apparent that the basement membrane zone remained attached to the basal cell layer of the epidermis, thereby forming the roof of the bullae. There was minimal inflammatory reaction in the dermis beneath the bullae. Lesions in the tongue and hard palate were similar to those in the skin. No mucosal lesions were detected elsewhere in the gastrointestinal tract. Electron microscopic examination of formalin-fixed specimens post fixed in 1% osmium tetroxide demonstrated that in areas of cleft formation the basal lamina remained attached to the basal cell layer of the epidermis (fig. 4); this confirmed the observations of light microscopy. No abnormalities were detected in either desmosomes or tonofilaments. The early onset of this disease in affected calves, together with the history of inbreeding, supports a genetic etiology, most likely characterized by recessive inheritance. Clinically and pathologically, the disease closely resembles the recessively inherited dermolytic bullous dermatosis reported in Dermal and oral ulceration was confined largely to areas exposed to friction; this suggested that trauma was necessary to initiate the development of bullae and the subsequent ulceration. Bullae clearly followed separation of the basal lamina from the underlying collagen. This disease in Brangus calves is clinically indistinguishable from familial acantholysis in Angus calve^,^ a disease which might be expected in Brangus cattle since this breed is partly based on the Angus genotype. Microscopically, however, there are distinct differences. Familial acantholysis is caused by defective formation of desmosome-tonofilament complexes that lead to separation (acantholysis) of cells within the basal and prickle cell layers of the epidermis. Abnormal whorls of tonofilaments appear as intracytoplasmic inclusion b ~ d i e s . ~ Such inclusions are not present in affected Brangus calves, and bullae originated by sub-basilar separation of the epidermis from the dermis, rather than by acantholysis (figs. 3, 4). Suffolk and South Dorset Down lambs with an epidermolysis bullosa had similar gross lesions to those in affected Brangus calves and, microscopically, bullae were seen to develop beneath the basal lamina.’ Cytoplasmic vacuolation in the epidermis and early cellular infiltration of the upper dermis were also described in affected lambs but were not seen in the Brangus calf. In collie dogs with epidermolysis bullosa simplex. skin lesions developed in association with frictional trauma, but were shown histologically to result from liquefactive degeneration of the basal cells of the epidermis, with the basal lamina forming the floor of bullae.’ The nature of the genetic defect in dermolytic bullous
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