Subacute sensory neuronopathy associated with Merkel cell carcinoma with unknown primary: a case report with literature review

Paraneoplastic neurologic syndromes (PNSs) are a wide spectrum of neurologic diseases characterized by different clinical features, associated with a neoplasia, and triggered by an immune-mediated process. In most cases, it is possible to detect specific neuronal antibodies and the Hu protein is one of the most frequently recognized intracellular antigens in patients with PNSs. Small-cell lung cancer is the most common cancer associated with PNSs, followed by urological, gynecological and hematological malignancies. Otherwise, extra-pulmonary small-cell carcinomas, including Merkel cell carcinoma (MCC), have been rarely described as related to PNSs. In this article we report, for the first time in the published literature, a case of anti-Hu antibody-related subacute sensory neuronopathy in association with MCC.