Kendra Leighten, mother of Everett, tells the story of their search for a diagnosis of his muscle problems. Everett was diagnosed at age 5 with GSD9d, one of the very rare muscle GSDs. There is little information available, but the deficient enzyme means that Everett does not produce myophosphorylase, the enzyme that is deficient in McArdle’s. It is thought that much of the advice about McArdle’s will apply to GSD9d.