FC‐26 Junctional epidermolysis bullosa in a Charolais calf with deficient expression of integrin α6β4

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Hereditary junctional epidermolysis bullosa (JEB) is a rare mechanobullous disease associated with defective expression of the hemidesmosome/anchoring filament proteins laminin‐5, collagen XVII and integrin α6β4. The condition is characterized by extensive blistering of the skin caused by splitting of the lamina lucida of the basement membrane (BM) in the squamous epithelia and by extracutaneous manifestations. Congenital JEB has been sporadically reported in cattle, but the BM protein associated with the genetic defect has not been identified. We report a case of spontaneous JEB in a 2‐week‐old female Charolais calf. Clinical lesions observed at birth were acral, auricular and oral erosions and ulcers, and onychomadesis of the four feet. General signs included anorexia, apathy, emaciation and marked cutaneous pain that justified rapid euthanasia. Histopathological examination revealed a dermo‐epidermal separation of the BM zone without keratinocyte cytolysis. Antigen immunomapping of frozen skin sections using antibodies to the major components of the human cutaneous BM revealed an intralamina lucida cleavage of the skin, which confirmed the diagnosis of JEB. In skin samples from the affected calf and wild type controls, the immunoreactivity of laminin‐5 and collagen XVII was comparable, while expression of integrin α6β4 was strongly reduced in the proband. These are the first results identifying itgα6 and itgβ4 as the candidate genes affecting cattle in JEB. They also suggest that altered expression of integrin α6β4 in ruminants is not associated with pyloric atresia – a complication always observed in humans suffering from altered synthesis of integrin α6β4. Funding: Self‐funded.