Fungal myelitis caused by Phialosimplex caninus in an immunosuppressed dog

A bone marrow infection caused by Phialosimplex caninus was diagnosed in a seven-year-old female spayed Cocker Spaniel that was receiving prednisone for autoimmune hemolytic anemia. Histopathologic examination of a bone marrow core biopsy revealed clusters of oval to round yeast-like cells of varying shape and size and occasional irregular hyphae. Culture of a bone marrow aspirate sample yielded a mould initially suggestive of Paecilomyces inflatus or Sagenomella species but later determined to be P. caninus. The dog was treated with itraconazole and amphotericin B, and prednisone was continued at the lowest dose needed to control the hemolytic anemia. The patient died after 18 months of treatment. This is the first detailed clinical report of infection caused by P. caninus, a newly described fungus associated with disseminated disease in dogs.