In the population of GSDs less than 6 years of age, 8 were homozygous mutant (A/A), 19 were heterozygous (G/A) and 23 dogs were homozygous wild type (G/G), which relates to an allele frequency of 0.35 for the SOD1:c.118A mutation in this GSD population. The gene discussed is SOD1; the disease is disorder of glycogen metabolism.