Test Detail

Recessive genodermatosis of the Chesapeake Bay Retriever (CBR) due to the absence of plakophilin-1 (PKP1) in the desmosomes of the superficial squamous epithelium. It produces severe skin fragility from birth with scaling and erosions in friction and mucocutaneous areas, together with partial hypotrichosis and deformed nails. The course is poor and most puppies are euthanized in the first months due to pain and the absence of curative treatment. It is the only described animal model of the human ectodermal dysplasia with skin fragility syndrome.

Specific to the Chesapeake Bay Retriever. The variant has also been detected in the Golden Retriever during routine genetic screening, according to OMIA:001864 (personal communication, without peer-reviewed publication). There are no population frequency data in CBR; the mutation appears to be concentrated in related lines.

- Skin fragility at birth with scaling of the superficial epithelium under pressure\n- Recurrent erosions and blisters in friction and mucocutaneous areas\n- Fine coat and patches of partial alopecia\n- Small and deformed nails\n- Thickening of footpads\n- Impaired growth and progressive emaciation\n- Euthanasia in most cases in the first months

Olivry and colleagues (2012) described the disease in nine CBR puppies from four litters born to eight related, clinically healthy breeding animals. Histology showed severe suprabasal acantholysis at birth that decreased with age, and electron microscopy showed scarce and malformed desmosomes with aggregated keratin filaments. Immunostaining revealed complete absence of plakophilin-1 and abnormalities in the distribution of desmoplakin and keratins 10 and 14. Sequencing identified a homozygous G>C mutation in the splice donor site of the first intron of PKP1 (c.202+1G>C), which produces a premature stop codon and a truncated protein of 75 amino acids instead of 749. The mutation co-segregated with the phenotype in the index family.

- Test breeding animals before mating with the PKP1 test, especially in CBR lines with a history of fragile skin or puppies euthanized for skin lesions\n- Do not cross two carriers: 25% risk of affected homozygotes\n- A carrier can be mated to a clear animal; offspring intended for breeding must be tested\n- In a CBR puppy with scaling at birth, suspect ED/SFS and confirm genetically\n- Progressively replace carriers with clear offspring without narrowing the gene pool

The differential diagnosis includes hereditary epidermolysis bullosa, juvenile pemphigus, dermatophytosis and cutaneous drug reactions. Histology with suprabasal acantholysis and electron microscopy with malformed desmosomes point toward ED/SFS. Immunostaining for PKP1 (absent in affected animals) confirms the pattern. There is clinical overlap with the human ectodermal dysplasia with skin fragility syndrome due to PKP1 mutations. The treatments described are symptomatic (skin care, topical antibiotics) and do not modify the course.

1. Olivry T et al. 2012. Deficient plakophilin-1 expression due to a mutation in PKP1 causes ectodermal dysplasia-skin fragility syndrome in Chesapeake Bay retriever dogs. PLoS One 7:e32072. PMID: 22384142
2. OMIA:001864-9615 - Ectodermal dysplasia/skin fragility syndrome, PKP1-related. https://omia.org/OMIA001864/9615/