Paraneoplastic opsoclonus-myoclonus syndrome secondary to melanoma metastasis form occult primary cancer

INTRODUCTION: Opsoclonus-myoclonus syndrome (OMS) is an inflammatory neurological disorder, often requiring a prompt medical evaluation. Among the diverse etiologies associated with OMS are autoimmune, infectious, paraneoplastic, and systemic diseases, and drug intoxication. CLINICAL SUMMARY: The case of a 36-year-old female with a disabling holocranial headache, sudden loss of consciousness, aggressive behavior, vertigo, and a personal history of somatoform disorder and major depression is presented here. After hospital admission, the patient developed sudden stereotyped movements in all four extremities and oculogyric crises compatible with OMS. Cerebrospinal fluid analysis, viral and autoimmune assays, as well as blood, urine, and bronchial secretion cultures, drug metabolite urinalysis, and tumor markers were all negative. Furthermore, brain computed tomography (CT) and brain magnetic resonance imaging, along with thoraco-abdominopelvic CT and electroencephalography, were also all negative. The patient suffered type one respiratory insufficiency after 72 h of hospitalization, requiring an endotracheal tube. After 13 days the patient suffered cardiac arrest. Necropsy was performed reporting lymph nodes with a poorly differentiated malignant neoplastic lesion, HMB-45, melan-A, vimentin, and S-100 positive, compatible with melanoma metastasis from an occult primary cancer. DISCUSSION: While the incidence of melanoma of unknown primary is between 2.6 and 3.2%, with a median overall survival ranging between 24 and 127 months, when melanoma patients develop OMS their survival is markedly decreased. Although only 5 cases of paraneoplastic OMS secondary to melanoma have been reported in the literature, all had a poor prognosis, dying within 8 months of OMS onset.