[Myasthenia gravis as paraneoplastic syndrome in small cell tumor of the bladder].

Only 0.48% of vesical tumours are of the small cells epithelial type with positive neuroendocrine immunohistochemical markers, although the description of new cases is becoming increasingly common. These tumours may be associated to paraneoplastic syndromes of the endocrine and neurological types. This paper contributes one case report of a female patient diagnosed with a small cells epithelial vesical tumour associated to myasthenia gravis. The histological and histochemical features as well as the differential diagnosis with other tumours of vesical location are explained. Clinically, these entities evolve with acute haematuria and have a highly aggressive evolution. Quite frequently the tumour is associated to neuromuscular syndromes such as Lamber-Eaton's, myasthenia-like syndromes, and in rare occasions to myasthenia gravis. Different studies have reported anti-acetylcholine receptors in cells of this tumoral class that may stimulate the formation of antibodies against the neuromotor plaque. Diagnosis of this neurological syndrome and other similar ones may be attributed to early treatment and better prognosis of this tumoral entity.