A 62-year-old woman with newly diagnosed ovarian cancer presents with progressive ataxia, nystagmus, and dysarthria. Serum anti-Yo antibodies are positive. Regarding paraneoplastic cerebellar degeneration (PCD), all of the following statements are true EXCEPT:

Question

Accepted Answer

A. Pathology shows selective loss of granule cells with relative preservation of Purkinje cells. ## Paraneoplastic Cerebellar Degeneration (PCD)

### Pathological Hallmark of PCD

**Key Point:** The pathognomonic finding in PCD is **loss of Purkinje cells** with relative preservation of granule cells — the opposite of what the distractor claims.

### Histopathological Features

| Cell Type | Status in PCD | Mechanism |
|-----------|---------------|----------|
| Purkinje cells | Severely depleted | Primary target of immune attack; express cdr1/cdr2 antigens |
| Granule cells | Relatively preserved | Secondary loss due to lack of Purkinje cell input |
| Molecular layer | Gliosis, inflammation | T-cell infiltration, cytotoxic response |

### Anti-Yo Antibodies and Mechanism

1. **Antigen Recognition:** Anti-Yo IgG binds to cdr1 (cerebellar degeneration-related antigen 1) and cdr2 on Purkinje cell cytoplasm
2. **Immune Mechanism:** CD8+ T-cell-mediated cytotoxic destruction of Purkinje cells
3. **Result:** Selective Purkinje cell loss → cerebellar ataxia, dysarthria, nystagmus

### Cancer Associations with PCD

**High-Yield:** Anti-Yo PCD occurs predominantly in:
- **Ovarian cancer** (50–80% of anti-Yo PCD cases)
- **Breast cancer** (10–30% of anti-Yo PCD cases)
- Rarely: endometrial, gastric, lung cancers

### Prognosis and Treatment

**Clinical Pearl:** Unlike some paraneoplastic syndromes, PCD is often **irreversible** even with cancer treatment or immunotherapy. However, early aggressive immunosuppression (corticosteroids, IVIG, plasmapheresis) may slow progression if initiated within weeks of symptom onset.

**Warning:** Delayed diagnosis and treatment lead to permanent neurological disability. The window for intervention is narrow.

Answer

B. Anti-Yo antibodies target Purkinje cell cytoplasmic proteins (cdr1 and cdr2)

Answer

C. Immunosuppressive therapy in early stages may halt disease progression

Answer

D. Ovarian and breast cancers account for the majority of PCD cases

A 62-year-old woman with newly diagnosed ovarian cancer presents with progressive ataxia, nystagmus, and dysarthria. Serum anti-Yo antibodies are positive. Regarding paraneoplastic cerebellar degeneration (PCD), all of the following statements are true EXCEPT:

Explanation

Paraneoplastic Cerebellar Degeneration (PCD)

Pathological Hallmark of PCD

Histopathological Features

Anti-Yo Antibodies and Mechanism

Cancer Associations with PCD

Prognosis and Treatment

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Cell Type	Status in PCD	Mechanism
Purkinje cells	Severely depleted	Primary target of immune attack; express cdr1/cdr2 antigens
Granule cells	Relatively preserved	Secondary loss due to lack of Purkinje cell input
Molecular layer	Gliosis, inflammation	T-cell infiltration, cytotoxic response