Based on the known function of PLA2G6 and its role in human and dog neurodegenerative disease, the rarity of the two identified variants in sheep and the perfect co-segregation of the variant alleles with the disease phenotype in the studied pedigree, we conclude that inherited NAD in Swaledale sheep is caused by compound heterozygosity for the two identified loss-of-function variants in PLA2G6. Thereby, this study provides another example for the occurrence of allelic heterogeneity causing Mendelian disorders in a livestock species. The gene discussed is PLA2G6; the disease is neurodegenerative disease.