It's been a long time since I've posted one of these random medical facts (just goes to show how little I get to study these days). I am now cramming for the neurology shelf, which is probably going to be quite challenging, since my knowledge base for neuroanatomy is pretty weak right now (it's been several years). I still have a few days, so we'll have to see how it goes.

LEMS is a autoimmune disease, with the the main symptoms being slowly progressive proximal muscle weakness with hyporeflexia. Autonomic dysfunction is often present as well, with dry mouth being the most common complaint. It can also be a paraneoplastic syndrome associated with small cell lung cancer. It is due to autoimmune attack against voltage-gated calcium channels (VGCC) on the presynaptic motor nerve terminal, causing impaired released of acetylcholine (ACh). Because the presynaptic stores of ACh and postsynaptic response remain intact, repetitive nerve stimulation actually improves symptoms (unlike in myasthenia gravis, where repetitive nerve stimulation causes muscle fatigue).

It is a clinical diagnosis, but can be confirmed with both VGCC antibodies and nerve conduction studies. The differential diagnosis is broad, covering any diseases which present with proximal muscle weakness, but the most common consideration is myasthenia gravis.

Therapy includes both symptomatic (guanidine, 3,4-DAP, pyridostigmine) and immunologic (plasma exchange, IVIG, oral immunosuppressive agents) options.