Pure white cell aplasia (PWCA) is a rare disorder of unknown origin, often associated with thymoma, characterized by selective neutropenia or pure agranulocytosis, and absence of granulocyte precursors in the bone marrow, but with normal erythroblasts and megakaryocytes. We report a case of PWCA associated with thymoma. Unusual findings in this case report included simultaneous presence of autoimmune thyroiditis, type 1 diabetes, anti-striated muscle antibodies, and the presence in the peripheral blood of CD8+ T cells that expressed a homogeneous naive phenotype. Neutrophil count became normal on immunosuppressive therapy after thymectomy.