Rare Association with Merkel Cell Carcinoma

Perineoplastic neurological syndromes associated with Merkel cell carcinoma are extremely rare, with only 30 cases previously reported in the literature, to which an additional 17 cases were added in a recent study. These disorders exhibit a heterogeneous clinical spectrum, with symptoms such as Lambert-Eaton Myasthenic Syndrome (LEMS) and rapidly progressive cerebellar syndromes. The immunological profile of affected patients also varies, prominently featuring antibodies such as HU, CB2, and voltage-gated calcium channels, which are linked to different manifestations of the syndromes. Notably, up to 50% of the patients demonstrated spontaneous primary tumor regression at the onset of perineoplastic neurological syndromes, shedding light on the complex relationship between tumor behavior and immune response in these cases.