Genetic basis - caused by a nonsense mutation (c.4579C>T, p.R1527) in the COL7A1 gene*. The COL7A1 gene encodes type VII collagen, a critical protein for anchoring the epidermis to the underlying dermis in skin. This mutation introduces a premature stop codon, leading to loss of functional collagen type VII protein. Inherited in an autosomal recessive manner; affected dogs have two copies of the mutation, carriers have one and are typically asymptomatic
Pathophysiology - Lack of type VII collagen disrupts the dermal-epidermal junction, causing skin layers to separate easily. Results in fragile skin prone to blistering, ulceration, and erosions with minimal trauma. Lesions primarily affect the feet, ears, muzzle, oral mucosa, and pressure points. Chronic wounds often become secondarily infected, complicating clinical course
Clinical Presentation - Clinical signs begin at birth or early puppyhood with widespread blisters and erosions. Affected puppies exhibit pain, reluctance to walk, bleeding, and difficulty eating due to oral lesions. The disease is severe and progressive; many affected dogs require euthanasia in early life due to poor quality of life
Inheritance - Autosomal recessive inheritance means both parents must be carriers to produce affected puppies. Carriers show no symptoms but can transmit the mutation to offspring.
Complications - Chronic skin wounds with risk of severe infections. Pain and impaired mobility due to skin lesions on feet and joints. Oral lesions may cause feeding difficulties. Progressive worsening often necessitates euthanasia.
Why This Matters to Breeders and Vets - is a severe, painful disorder drastically affecting affected dogs’ welfare. Genetic testing for the COL7A1 mutation allows breeders to identify carriers and avoid at-risk matings. Early diagnosis supports appropriate management and breeding decisions to reduce prevalence