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Antineuronal Nuclear Antibody Type II (Anti-Ri)

Anti-Ri is the least common of the paraneoplastic autoantibodies. Detection of Anti-Ri antibody in serum or spinal fluid identifies an otherwise unexplained neurological disorder as autoimmune and paraneoplastic. A positive result prompts a search for an underlying occult malignancy. Anti-Ri antibodies are detected most commonly in postmenopausal women who usually present with signs of midbrain, brain stem, cerebellar and/or spinal cord dysfunction. Ocular opsoclonus-myoclonus may be a prominent symptom. Most patients have a primary carcinoma of the breast. Lung and gynecological cancer are less frequently associated with this syndrome. Treatment of the cancer can lead to decreased antibody titer and improvement of the neurological disorder. A negative result does not rule out cancer. Anti-Ri antibodies are seldom detected in patients with breast carcinoma who do not have neurological dysfunction.

Specimen requirement is one red top or SST tube of blood or CSF.

Reference Range is <1:60 for serum and <1:2 for spinal fluid.

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