Lethal Acrodermatitis (LAD) in Bull Terriers and Miniature Bull Terriers

Lethal Acrodermatitis (LAD) is a genodermatosis i.e. a serious inherited skin condition of Bull Terriers and Miniature Bull Terriers. It is a complex immune deficiency that is caused by defective zinc metabolic pathway or zinc absorption.

The disease is characterized by severe retardation of growth and development, immune deficiency and characteristic skin lesions. Unpleasant lesions and swelling appear especially on the muzzle, around the eyes and ears.  The skin on the feet is hard and cracked and crusted skin lesions and cracks develop on the footpads. The disease is often accompanied with diarrhoea and pneumonia. The LAD affected dogs show signs of coat colour dilution in pigmented skin areas. The clinical signs of LAD appear after the first week from the birth of the puppies. The puppies affected by mutation grow slower, are weaker and less active and by one year of age their weight and size is half the weight and size of a healthy dog.  The affected dogs usually die before they reach two years of age and that due to infection (in case of bronchopneumonia) or they are euthanized because of severe and painful lesions on the feet.

LAD is caused by mutation chr14: 5,731,405T>G (also MKLN1: c.400 + 3A>C) that has been localized on  ~ 1,11 MB segment of 14th  chromosome in MKLN1 gene. Due to this mutation the exon 4 is skipped in the MKLN1 transcripts of the LAD affected dogs, which leads to a shift of the reading frame and to a change of properties of the protein produced.  MKLN1 encodes the widely expressed intracellular protein muskelin 1, which has diverse functions in cell adhesion, morphology and intracellular transport processes.

The genetic test can reveal the genotype of the given dog and prevent unintentional production of LAD affected dogs.

LAD is inherited as an autosomal recessive trait. That means the disease affects dogs with P/P (positive / positive) genotype only. The dogs with P/N (positive /negative) genotype are clinically without any symptom. They are genetically considered carriers of the disease (heterozygotes). In offspring of two heterozygous animals following genotype distribution can be expected: 25 % N/N (healthy non-carriers), 25 % P/P (affected), and 50 % N/P (healthy carriers). Because of high risk of producing affected offspring, mating of two N/P animals (carriers) can not be recommended.

.

Reference:

Bauer A, Jagannathan V, Högler S, Richter B, McEwan NA, Thomas A, et al. (2018) MKLN1 splicing defect in dogs with lethal acrodermatitis. PLoS Genet 14(3): e1007264.