Autoimmune paraneoplastic cerebellar degeneration: Ultrastructural localization of antibody-binding sites in purkinje cells

Sera from three of four patients with paraneoplastic cerebellar degeneration (PCD) associated with gynecologic cancer had antibodies that stained the cytoplasm of Purkinje cells in a characteristic discrete and coarsely granular pattern. No such antibodies were found in PCD patients with small cell cancer of the lung, in patients with cerebellar degeneration without cancer, in nonneurologic patients with small cell carcinoma or gynecologic cancer, or in normal subjects. Immunoelectron microscopy revealed that the antibodies of PCD bound to clusters of ribosomes, granular endoplasmic reticulum, and the trans-face of the vesicles of the Golgi complex in Purkinje cells. Immunostaining was localized in orderly arrays of stacked parallel cisternae of the endoplasmic reticulum in the perikaryon and dendritic processes. This pattern suggested that at least one autoantigen of PCD may be a glycoprotein specific for cerebellar tissue that is associated with the endoplasmic reticulum. Some patches of Purkinje plasma membrane also were immunostained.