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

Abstract

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 <125 mmol/L) coincident with MCC was identified among 4.3% (9 of 211) patients with MCC in the Kaiser Permanente Northern California cohort.

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.

Keywords: Lambert-Eaton myasthenic syndrome; Merkel cell carcinoma; cerebellar degeneration; malignancy-associated hyponatremia; neuroendocrine; paraneoplastic syndrome.