[Paraneoplastic diseases of the motor end-plate and muscle]

Some forms of myasthenia gravis and many cases of Eaton-Lambert syndrome are disorders of neuromuscular transmission possibly of paraneoplastic origin. Paraneoplastic necrotizing myopathy and some cases of inflammatory myopathy (polymyositis-dermatomyositis) are paraneoplastic myopathies.

These are all autoimmune processes. The diagnosis is clinical, based mainly on the characteristics of the muscle weakness and motor disorders, confirmed by serological methods (demonstration of antibodies) pharmacological and electromyographic tests, by imaging studies and in some cases biopsy. Treatment includes specific symptomatic measures (aimed at correcting the defect in neuromuscular transmission in the myasthenic syndromes, reducing axonal auto-excitability in the neuromuscular hyperexcitability syndromes, etc.) and pathogenic treatment (basically immunosuppression). A search for the hidden tumour should also be part of the diagnostic investigation. The paraneoplastic disease may remit if the associated tumour is treated.