Antibodies to calcium channel are seen in

Lambe-Eaton syndrome presents with proximal muscle weakness that improves with exercise & is caused by the development of antibodies to presynaptic calcium channels. Myasthenia gravis is autoimmune disease caused by the development of antibodies to postsynaptic acetylcholine receptors.Polymyositis & Dermatomyositis are related disorders that are characterised by an inflammatory process affecting skeletal muscle. In dermatomyositis,characteristic skin changes also occur. Davidson's Medicine-22nd edition,page no:272,1114,1226,1227