Our patient worked as a forester. He drank a moderate amount of Japanese sake and had quit smoking 10 years prior. Of note, he had been growing shiitake mushrooms in his garden for five years, and he ate them almost every day, especially in spring and autumn, the harvest season. He ate two to three mushrooms a day on average.
A physical examination showed his vital signs were within normal limits. Auscultation of lungs and heart was normal. He had muscle tenderness over his back and both thighs. Manual muscle testing revealed mild weakness only in the hip flexors (4/5 on the medical research council scale), but he had normal strength in the rest of his muscles.
On laboratory tests (see Table 1), his serum CK level was 1,280 IU/L. Anti-nuclear antibody immunofluorescence staining showed cytoplasmic pattern (1:80). Anti-Jo-1 and other selected autoantibodies were negative.