Pathophysiology Cancer Clinical Scenario Question

Question

A 48-year-old man presents at his health care clinic with complaints of leg weakness. He is a heavy smoker and has had a productive cough for years. Subsequent diagnostic tests reveal he has a small cell lung cancer with brain metastasis. His proposed plan of treatment includes chemotherapy and radiation therapy. 

1. What is the probable cause for leg weakness in this patient, and is it related to the lung cancer?

Does anyone know the answer to this? I was thinking it was probably due to the chemo and radiation.

Answer 1

Assuming he has true muscle weakness, rather than just feeling tired and having little stamina, he likely has Lambert Eaton syndrome which is most commonly associated with small cell lung cancer. The weakness is caused by an automimmune loss of voltage gated presynaptic calcium channels. This interrupts signaling for the release of neurotransmitter by the neurons of the neuromuscular junction.