Paraneoplastic syndromes (PNS) associated with Merkel cell carcinoma (MCC): A case series of 8 patients highlighting different clinical manifestations

Background Paraneoplastic syndromes (PNS) are commonly associated with neuroendocrine cancers, such as small cell lung cancer. Objectives We examined the association of PNS in Merkel cell carcinoma (MCC), a rare neuroendocrine skin cancer. Methods We identified PNS associated with MCC based on chart review of a Seattle-based repository and examined the incidence of MCC-associated hyponatremia in an independent cohort within Kaiser Permanente Northern California. Results Eight PNS cases were identified from the Seattle repository. Three distinct PNS types were observed: cerebellar degeneration (1 case), Lambert-Eaton myasthenic syndrome (2 cases), and malignancy-associated hyponatremia (5 cases). Moreover, the incidence of severe hyponatremia (serum sodium Limitations We did not have access to complete medical records on all patients so it was not possible to determine the prevalence of PNS in MCC. Conclusions MCC can be associated with PNS similar to those found in other neuroendocrine cancers. Clinicians should be aware of these presentations as PNS often precede the identification of the underlying malignancy and usually resolve with appropriate treatment of the cancer.