Jaw Dystonia and Myelopathy: Paraneoplastic Manifestations of Breast Malignancy with anti-Ri/ANNA-2 Antibody

Paraneoplastic neurologic syndrome associated with gynecologic and breast malignancies

Gynecologic and breast malignancies are the cancers most commonly associated with paraneoplastic neurologic syndromes, of which the foremost is Yo [Purkinje cell antibody, type 1 (PCA-1)] paraneoplastic cerebellar degeneration. Yo syndrome affects women in the sixth decade and manifests as a subacute severe cerebellar ataxia. The association of the typical clinical picture with the detection of Yo antibodies in a patient's serum or CSF defines the diagnosis. Yo syndrome is always associated with a cancer, and the search for the underlying tumor should focus on ovarian and breast cancers and be repeated overtime if negative. The Yo autoantibodies are directed against the Yo antigens, aberrantly overexpressed by tumor cells with frequent somatic mutations and gene amplifications. The massive infiltration of these tumors by immune cells suggests that they are the site of the immune tolerance breakdown, leading to the destruction of Purkinje cells harboring the Yo antigens. Despite a growing understanding of the immunologic mechanisms, efficient therapeutic options are still lacking. Anti-Ri and antiamphiphysin syndromes are rarer and associated with breast cancers; a wide variety of other rare paraneoplastic neurologic syndromes have been described in association with gynecologic and breast malignancies that, though sharing some similarities, may have specific immune and genetics features leading to the immune tolerance breakdown.

Paraneoplastic antibodies targeting intracellular antigens

Although they are relatively rare, the diagnosis of paraneoplastic neurologic syndromes (PNS) can be aided by the identification of neural autoantibodies in patients' serum and cerebrospinal fluid (CSF). They often clinically manifest as characteristic syndromes, including limbic encephalitis, opsoclonus-myoclonus syndrome, paraneoplastic cerebellar degeneration, and paraneoplastic encephalomyelitis. The antibodies are directed either toward intracellular targets, or epitopes on the cell surface. As compared to cell surface antibodies, intracellular paraneoplastic autoantibodies are more classically associated with cancer, most often lung, breast, thymoma, gynecologic, testicular, and/or neuroendocrine cancers. The malignancies themselves tend to be small and regionally contained, attesting to the strength of the immune system in cancer immunosurveillance. Typically, the intracellular antibodies are not directly pathogenic and tend to be associated with PNS that are poorly responsive to treatment. With some notable exceptions, including patients with PNS associated with testicular cancer, patients with intracellular antibodies are typically older individuals, in their 7th decade of life and beyond. Many of them are current or former smokers. Treatment strategies include tumor removal as well as immunotherapy to treat the concomitant PNS. Newer technologies and the ever-broadening use of cancer immunotherapies are contributing to the continued identification of novel intracellularly targeted autoantibodies.

Update in autoimmune and paraneoplastic myelopathies: Newly described antigen targets and antibody testing

Myelopathy is an increasingly recognized presentation of many antibody-mediated neuroinflammatory disorders. While specific features of certain autoimmune myelopathies such as aquaporin-4 antibody associated neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein associated disorder (MOGAD) are well-characterized, other less commonly seen antibody-associated myelopathies are not as well-defined. These include but are not limited to, Hu/ANNA1, anti-glial fibrillary acidic protein (GFAP), anti-CV2/collapsin response mediator protein (CRMP5), and amphiphysin. Here, we review the mentioned more common antibody mediated myelopathies as well those that as less common, followed by a review of differentials that may mimic these disorders.