Lambert-Eaton myasthenic syndrome (LEMS) is associated with small cell lung cancer as a paraneoplastic phenomenon. There is a decrease in the expression of voltage gated calcium channels (VGCC) on presynaptic nerve terminals due to presence of an autoantibody. The tumour cells also express this antigen.
Lambert-Eaton myasthenic syndrome (LEMS) associated with small cell lung.
Presence of VGCC antibodies has a sensitivity of >90% for LEMS associated with primary lung cancer and around 40% assocaited with small cell lung cancer. Up to 40% of LEMS patients have no sign of the primary cancer on diagnosis but it develops in 2-4 years.
Radioimmunassay: Antibodies block binding of radiolabelled w-conotoxin to membrane receptor preparations.
Referred test: only available to Neurology staff.
Assay range notes
Results\expressed as pM of bound toxin. Values above 100pM are considered as\ positive. Under 45pM are negative.
Churchill Hospital Department of Immunology