Anti-Yo Positive Case Studies
Recent case reports demonstrate that anti-Yo antibody positivity presents most commonly as paraneoplastic cerebellar degeneration in middle-aged to elderly women with gynecologic malignancies, though rare atypical presentations with benign tumors and delayed onset have been documented.
Classic Presentations
Ovarian Cancer with Delayed Onset
A case from 2025 describes an elderly woman who developed subacute cerebellar symptoms three years after ovarian cancer resection, ultimately diagnosed with anti-Yo positive PCD 1. Despite immunotherapy, her ataxia showed only limited improvement, suggesting irreversible pathological progression. This challenges the conventional understanding that PCD typically precedes tumor detection.
Breast Cancer with Prolonged Prodrome
A 46-year-old woman presented with progressive gait instability, dysarthria, and nystagmus with cerebellar atrophy on MRI and strong anti-Yo positivity 2. The underlying HER2-positive invasive ductal breast carcinoma was not diagnosed until two years later. Despite modified radical mastectomy, adjuvant chemotherapy, and trastuzumab, her neurological symptoms persisted and worsened progressively.
Occult Nodal Metastases
A 56-year-old woman developed gradually worsening cerebellar dysfunction over months with high-titer anti-Yo antibodies in both serum and CSF 3. FDG-PET/CT identified pelvic lymph nodes containing metastatic clear cell carcinoma, though the primary gynecologic organs (uterus, ovaries, fallopian tubes) were entirely benign. After plasma exchange, IVIG, steroids, and carboplatin/paclitaxel, she achieved some improvement in speech and upper-limb coordination but remains non-ambulatory three years later.
Atypical Presentations
Limbic Encephalitis with Benign Adenoma
The first documented case of anti-Yo positive limbic encephalitis (rather than typical cerebellar degeneration) involved a 59-year-old male presenting with epileptic seizures, left upper limb weakness, dysarthria, and confusion 4. The associated tumor was a benign thyroid-parathyroid adenoma, not the expected malignancy. MRI showed diffusion restriction in cerebellar hemispheres and middle cerebellar peduncles. High-dose methylprednisolone followed by IVIG resulted in clinical improvement.
Male Patient with Favorable Response
A 64-year-old man presented with progressive ataxia, gait instability, and dysuria with anti-Yo detected in serum but not CSF 5. After dexamethasone failed, four courses of plasma exchange resulted in independent ambulation and undetectable anti-Yo antibodies at 6-month follow-up. This represents one of fewer than 20 reported male cases and demonstrates that plasma exchange may be effective in non-tumor-associated cases.
Prognostic Insights from Cohort Data
A 2026 cohort study of 19 seropositive autoimmune cerebellar ataxia patients found that 11 (57.9%) were anti-PCA-1 (Yo) positive, and all were paraneoplastic 6. Key findings:
- Tubo-ovarian serous carcinoma was most common (63.6%)
- 90.9% were female
- 100% became wheelchair-dependent despite treatment
- Acute onset (<2 weeks) and PCA-1 positivity predicted wheelchair dependence
- The Brief Ataxia Rating Scale (BARS) monitored symptoms more precisely than mRS or CASE
Clinical Pearls
Common pitfalls to avoid:
- Don't assume neurological symptoms will improve with cancer treatment alone—most patients have irreversible cerebellar damage
- Don't limit cancer screening to initial CT; consider pelvic ultrasound/MRI for ovarian pathology and FDG-PET for occult malignancies 7
- Don't dismiss the diagnosis in males or with atypical presentations like limbic encephalitis
- Don't delay immunotherapy while awaiting tumor identification—early treatment may preserve function 4
The guideline recommends that female patients with ataxic presentation suggestive of PCA1/Yo antibody should undergo pelvic ultrasound screening for ovarian carcinoma 7. When initial screening is negative but suspicion remains high, whole body FDG-PET scan should be pursued.