Introduction: Amyotrophic lateral sclerosis (ALS) is a form of motor neuron disease that primarily affects upper and lower motor neurons. Its etiology is unknown, it has a progressive course and is often fatal. Very rarely, its appearance as paraneoplastic syndrome (PNS) has been described. Certain clinical patterns of motor neuron disease suggest this association. The anti-CV2 are a type of onconeuronal antibody, invariably associated to tumor and described in different PNSs as paraneoplastic encephalomyelitis, cerebellar degeneration and peripheral neuropathy.
Clinical case: 29 years old male with criteria of probably ALS. Due to his atypical onset (patient's age), onconeuronal antibodies were requested, detecting anti- CV2+. After three years of follow-up and exhaustive search for tumors, with progression of the disease, there is currently no evidence of associated cancer.
Discussion: The study of the motor neuron/ALS disease as paraneoplastic syndrome, due to its rareness, has led to reviews in order to verify this relationship. When ALS exists, we should rule out association to tumor when the presentation is early (< 30 years) or late (> 70 years), when it is associated to other neurological symptoms/signs (sensory symptoms, ataxia, etc.), when anti-Hu antibodies or others are present and/or when there is paraproteinemia and/or pleocytosis-high protein levels in cerebral spinal fluid. We present a case of probable ALS with anti-CV2+, with no evidence of underlying cancer. After an extensive bibliographic search, we have found no description of this association. We also have no knowledge of the existence of anti-CV2 antibodies outside of the tumor context, so that we believe that our patient probably has an occult neoplasm.