21st February 2025

A 59-year-old woman presents with a 1-month history of leg weakness and difficulty walking on a background of 3 months of fatigue and weight loss.

A 59-year-old woman presents with a 1-month history of leg weakness and difficulty walking on a background of 3 months of fatigue and weight loss. She has also noted a dry mouth and some visual difficulties. On examination, she is noted to have proximal muscle weakness of the limbs, which initially improves with exercise but then worsens as exercise continues. She has a ‘waddling’ gait and reduced deep tendon reflexes. She is also found to have significant postural hypotension. Imaging of the chest demonstrates a lung nodule. 

Which is the most likely underlying pathology?

Select the SINGLE most appropriate option from the list below. Select ONE option only.