Paraneoplastic progressive Supranuclear palsy: a case report and literature review.

Progressive supranuclear palsy-Richardson syndrome (PSP-RS) is a sporadic atypical parkinsonian disorder typically resistant to levodopa. While most cases are neurodegenerative, various conditions (genetic, vascular, infectious, or paraneoplastic) can mimic this phenotype, termed PSP-like or PSP mimics. Although paraneoplastic PSP is extremely rare, it is important to recognize because of its potential reversibility. The diagnosis can be particularly challenging, especially when classical tumor markers or imaging fail to identify a clear neoplastic origin. Here, we describe a 39-year-old man with an Anti-Ri-mediated PSP-like syndrome in whom an extensive evaluation, including surgical removal of two suspicious sites (thymus and testis), failed to identify an underlying tumor. The patient presented with rapidly progressive symptoms characteristic of PSP-RS, raising clinical suspicion for a paraneoplastic cause. We also review the literature on paraneoplastic PSP.