Anti-Yo (PCA1) Antibody Associated Paraneoplastic Cerebellar Degeneration (PCD) in Primary Occult Breast Cancer (OBC).
Daniel Moreira1, Juan Cabrera Pulla1, Hamza Coban2, Alexis Demopoulos3
1Neurology, University of Connecticut Health/Hartford Hospital, 2Neurology, University of Connecticut Health, 3Neurology, Hartford Hospital
Objective:

To encourage exhaustive neoplastic workup when clinically classic paraneoplastic cerebellar degeneration (PCD) presents.

Background:
Occult breast cancer (OBC) comprises only 0.1-3% of breast cancer patients presenting without detectable primary breast mass and distant metastases, often involving axillary lymph nodes. Anti-Yo (PCA1) antibody associated PCD may precede the diagnosis of cancer by years or arise with limited stage neoplasm, including HER-2 expressing breast carcinomas.
Design/Methods:
Case report/literature review.
Results:

Following a nonspecific prodrome of dizziness lasting one month, a 57-year-old female presented with three months of gait instability, dysarthria, and memory difficulties. Neurological examination revealed memory and attention deficits, difficulty naming objects, tangential speech, wide-based gait, reduced saccadic velocities, and appendicular dysmetria. Brain MRI was normal. Seven nucleated cells were found on CSF analysis with 92% lymphocytes, elevated protein (48 mg/dL), normal glucose (64 mg/dL), and negative cytology. An elevated IgG index (1.45) and oligoclonal bands were present. CT chest/abdomen/pelvis identified a suspicious 1.1 cm right axillary lymph node, while breast examination, mammogram, ultrasound, and breast MRI revealed no disease. Whole-body PET showed the axillary node was FDG-avid. Biopsy demonstrated HER-2 positive adenocarcinoma suspicious for breast origin. Serum and CSF contained anti-Yo antibodies.

Following five days of intravenous methylprednisolone and immunoglobulin, gross total resection of the right axillary lymph node, and chemotherapy with carboplatin, trastuzumab, and pertuzumab, her cognitive symptoms nearly resolved, and coordination improved four months later.

Conclusions:
Rapidly progressive cerebellar ataxia is a “classic” presentation of PCD and association with CSF oligoclonal bands should prompt aggressive neoplastic workup. Our experience suggests rapid immunomodulation initiation, including antigen reduction, may lead to improved outcomes. 
10.1212/WNL.0000000000210343
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