Lung Cancer: The Daily PANCE Blueprint
A 55-year-old man presents to the neurology clinic complaining of progressive weakness in his proximal muscles. Over the past six months. He reports difficulty climbing stairs and rising from a seated position. Recently, he has also noticed a dry mouth and intermittent diplopia. His medical history is notable for a 30-year history of smoking. Physical examination reveals diminished deep tendon reflexes and muscle strength that improves with repeated testing. Which of the following is the most likely diagnosis?
A. Myasthenia Gravis
B. Multiple Sclerosis
C. Eaton-Lambert Syndrome
D. Amyotrophic Lateral Sclerosis
E. Guillain-Barré Syndrome
Answer and topic summary
The answer is C. Eaton-Lambert Syndrome
Eaton-Lambert syndrome, often associated with small cell lung cancer (particularly in smokers), is characterized by muscle weakness that predominantly affects the proximal limbs. It is a paraneoplastic syndrome resulting from antibodies directed against presynaptic calcium channels, leading to reduced acetylcholine release. Unlike myasthenia gravis, muscle strength and reflexes in Eaton-Lambert syndrome typically improve with repeated testing, aligning with this patient’s presentation.
Explanation for Incorrect Answers:
- A. Myasthenia Gravis: This autoimmune disorder also presents with muscle weakness and can involve ocular muscles leading to diplopia. However, muscle weakness in myasthenia gravis typically worsens with activity, contrary to the improvement with activity noted in Eaton-Lambert syndrome.
- B. Multiple Sclerosis: A central nervous system disorder that can cause muscle weakness but is more commonly associated with sensory deficits, visual problems, and acute episodes of neurological dysfunction (relapses), which do not match this patient’s primary complaints.
- D. Amyotrophic Lateral Sclerosis: This motor neuron disease leads to progressive muscle weakness, including both upper and lower motor neuron signs (such as muscle wasting and hyperreflexia), without the characteristic improvement with activity seen in Eaton-Lambert syndrome.
- E. Guillain-Barré Syndrome: Typically presents as an acute polyneuropathy with ascending muscle weakness and areflexia, often following an infectious illness. It does not show the improvement with repeated muscle use seen in Eaton-Lambert syndrome.
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Smarty PANCE Content Blueprint Review:
Covered under ⇒ PANCE Blueprint Pulmonary => Neoplasms => Lung cancer
Also covered as part of the Family Medicine EOR and Emergency Medicine EOR topic lists
