A congenital bovine epidermolysis resembling epidermolysis bullosa simplex of man

A de novo mutation in KRT5 in a crossbred calf with epidermolysis bullosa simplex

A 6‐day‐old Belgian Blue‐Holstein calf was referred because of a syndrome resembling epidermolysis bullosa simplex (EBS). The clinical phenotype included irregular and differently sized erosions and ulcerations spread over the body, in particular on the limbs and over bone prominences, as well as in the nasal planum and oral mucosa. Blisters were easily induced by rubbing the skin. The skin lesions displayed a clear dermal‐epidermal separation at the level of the basal cell layer. Post mortem examination revealed erosions in the pharynx, proximal esophagus, and rumen. Whole‐genome sequencing revealed a heterozygous disruptive in‐frame deletion variant in KRT5 (c.534_536delCAA). Genotyping of both parents confirmed the variant as de novo mutation. Clinicopathological and genetic findings were consistent with the diagnosis of KRT5‐related EBS providing the second example of a spontaneous mutation causing epidermolysis bullosa in cattle.

Epidermolysis bullosa in Danish Hereford calves is caused by a deletion in LAMC2 gene

BACKGROUND

Heritable forms of epidermolysis bullosa (EB) constitute a heterogeneous group of skin disorders of genetic aetiology that are characterised by skin and mucous membrane blistering and ulceration in response to even minor trauma. Here we report the occurrence of EB in three Danish Hereford cattle from one herd.

RESULTS

Two of the animals were necropsied and showed oral mucosal blistering, skin ulcerations and partly loss of horn on the claws. Lesions were histologically characterized by subepidermal blisters and ulcers. Analysis of the family tree indicated that inbreeding and the transmission of a single recessive mutation from a common ancestor could be causative. We performed whole genome sequencing of one affected calf and searched all coding DNA variants. Thereby, we detected a homozygous 2.4 kb deletion encompassing the first exon of the LAMC2 gene, encoding for laminin gamma 2 protein. This loss of function mutation completely removes the start codon of this gene and is therefore predicted to be completely disruptive. The deletion co-segregates with the EB phenotype in the family and absent in normal cattle of various breeds. Verifying the homozygous private variants present in candidate genes allowed us to quickly identify the causative mutation and contribute to the final diagnosis of junctional EB in Hereford cattle.

CONCLUSIONS

Our investigation confirms the known role of laminin gamma 2 in EB aetiology and shows the importance of whole genome sequencing in the analysis of rare diseases in livestock.

Epidermolysis bullosa in animals: a review

Epidermolysis bullosa (EB) is a hereditary mechanobullous disease of animals and humans, characterized by an extreme fragility of the skin and mucous membranes. The main feature of EB in humans and animals is the formation of blisters and erosions in response to minor mechanical trauma. Epidermolysis bullosa is caused by mutations in the genes that code for structural proteins of the cytoskeleton of the basal keratinocytes or of the basement membrane zone. Based on the ultrastructural levels of tissue separation, EB is divided into the following three broad categories: epidermolysis bullosa simplex, junctional epidermolysis bullosa and dystrophic epidermolysis bullosa. Human types of EB are divided into several subtypes based on their ultrastructural changes and the mode of inheritance; subtypes are not fully established in animals. In humans, it is estimated that EB affects one in 17,000 live births; the frequency of EB in different animals species is not known. In all animal species, except in buffalo with epidermolysis bullosa simplex, multifocal ulcers are observed on the gums, hard and soft palates, mucosa of the lips, cheek mucosa and dorsum of the tongue. Dystrophic or absent nails, a frequent sign seen in human patients with EB, corresponds to the deformities and sloughing of the hooves in ungulates and to dystrophy or atrophy of the claws in dogs and cats. This review covers aspects of the molecular biology, diagnosis, classification, clinical signs and pathology of EB reported in animals.

Inherited junctional epidermolysis bullosa (Herlitz type) in German black-headed mutton sheep

This report describes the microscopical, immunohistochemical and ultrastructural findings in the first ovine cases of the Herlitz type of inherited junctional epidermolysis bullosa. Sixteen German black-headed mutton lambs and one crossbred lamb had blisters and ulceration of the skin and mucous membranes in addition to alterations of the horn of the hooves. Microscopically, there was separation of the dermoepidermal junction, which was confirmed to be located in the lamina lucida of the basement membrane by electron microscopy. In areas of subepidermal splitting the hemidesmosomes were missing and in adjacent areas they appeared to be rudimentary and reduced in number. Immunohistochemistry for laminin 5 revealed a markedly reduced expression of this molecule on the dermal side of the blisters, while expression of collagen VII was normal.

Junctional epidermolysis bullosa in a calf

A case of epidermolysis bullosa in a calf descendent from a Gir bull and a Gir crossbreed cow is reported. The calf presented with exungulation of all hooves, widespread erosions and crusts on the skin, and ulcers in the oral cavity. Histologically, the skin showed subepidermal separation with clefts occasionally filled with eosinophilic clear fluid, cellular debris, or neutrophils. Ultrastructurally, there was epidermal-dermal separation at the level of the lamina lucida, with the lamina densa attached to the papillary dermis. The hemidesmosomes were poorly defined and small. The clinical, histological, and ultrastructural findings are characteristic of junctional epidermolysis bullosa.

Epidermolysis bullosa in calves in the United Kingdom

Epidermolysis bullosa (EB) was diagnosed in eight calves from four farms in the United Kingdom on the basis of clinical, histological and ultrastructural findings. In three affected herds, pedigree Simmental bulls had been mated with Simmental-cross cows. In a fourth herd two Holstein-Friesian calves were affected. Lesions included multifocal erosion and ulceration of the hard and soft palates, tongue, nares and gingiva, with onychomadesis (dysungulation). There was alopecia, erosion and crusting of the coronets, pasterns, fetlocks, carpi, hocks, flanks and axillae. Histopathological findings included segmental separation of full thickness epidermis from the dermis, with formation of large clefts containing eosinophilic fluid, extravasated red blood cells and small numbers of neutrophils. Follicular and interfollicular areas of skin were affected, with clefts extending around hair follicles and sometimes involving whole follicles. Ultrastructurally, there was evidence of vacuolar change within basal keratinocytes, corresponding to areas of histological clefting. Preliminary genetic screening of the candidate keratin genes (bKRT5 and bKRT14) has excluded mutations of these as the cause of this condition.

Dystrophic form of inherited epidermolysis bullosa in a dog (Akita Inu)

We report a dog with dystrophic epidermolysis bullosa. This 4-year-old female Akita Inu, a species of Canis familiaris var. japonicus Temminck, had a 3-year-history of ulcers and scars over the pressure areas on the limbs, and dystrophic nails, since the age of 1 year, which corresponds to early adulthood in humans. Electron microscopy of a blister revealed separation beneath the lamina densa, and a reduction in the number of anchoring fibrils. The NC-1 domain of type VII collagen was positively stained with monoclonal antibody LH7.2 at the basement membrane zone. These findings indicate that humans and dogs have a similar response to antibody LH7.2, which may aid the development of an animal model for this disease.

Hereditary suprabasilar acantholytic mechanobullous dermatosis in buffaloes (Bubalus bubalis)

A skin disease characterized by trauma-induced sloughing of haired skin, hooves, and horns is described in four calves from a herd of Murrah buffaloes (Bubalus bubalis) in Brazil. Affected calves were detected shortly after birth by the presence of lesions affecting the distal extremities, the scapular and gluteal regions, and the tip of the tail. On histologic evaluation of affected skin, the lesions were characterized by suprabasilar vesicles and acantholysis affecting the epidermis and outer root sheath of the hair follicle infundibulum. The basal cell layer was intact and appeared as a single layer of cuboidal cells attached to the dermis. Ultrastructurally, the region between the stratum basale and the lower stratum spinosum had widened intercellular spaces with loss of desmosomal attachments, which led to the suprabasilar separation. The disease appears to be inherited as an autosomal recessive trait.

Congenital generalized epidermolysis bullosa in a calf

Epidermolysis bullosa is reported in a newborn calf. The disorder was lethal due to the large extension and severity of the skin lesions. Histopathologically, the defect was characterized by suprabasilar clefts located in stratum spinosum. In large areas, most epidermal layers were lost exposing stratum basale or even dermis. The basal membrane seemed normal. The disorder shared features with previous reported cases of both epidermolysis bullosa and familial acantholysis. The aetiology was not determined.

Immunohistochemistry of parasitic subepidermal vesiculobullous disease in American badgers (Taxidea taxus)

Some populations of free-ranging American badgers (Taxidea taxus) develop a distinctive seasonal dermatitis due to the subcutaneous filariid Filaria taxideae. Subepidermal vesicles that contain filarial ova develop in thinly haired skin of the inguinal area, proximal thigh, and ventral abdomen. The purpose of this study was to establish by immunohistochemistry whether basement membrane components colocalized with the roof or floor of vesicles and to confirm that filarial ova occur in intradermal vessels. Samples of skin with characteristic F. taxideae-induced subepidermal vesicles were collected from 10 adult male (n = 8) and female (n = 2) badgers. Samples were fixed in formalin for 1-4 days and processed routinely into paraffin wax. Immunohistochemical staining for basement membrane was attempted with anti-collagen IV antibodies (AM168-5M, AR079-5R, AB748) and antilaminin antibodies (MA078-5C, AR078-5R, L-9393). Optimal results in skin from badgers were obtained using a biotin-streptavidin technique and AR079-5R (anti-human collagen IV) and AR078-5R (anti-murine laminin). There was positive staining of the floor of vesicles in 5 of 6 badgers tested with antibodies to laminin and collagen IV. In 5/10 badgers, filarial ova and first stage F. taxideae larvae were found in dilated vascular channels of the upper dermis, and these vessels stained positively for factor VIII-related antigen. The results suggest that F. taxideae-induced subepidermal separation occurs consistently in the lamina lucida portion of the basal lamina and that filarial ova occur in dermal vessels.