The most characteristic feature of Myasthenia Gravis is?

SCTIMST Staff Nurse - 2016

Medical & Surgical Nursing

Easy

Appeared in: SCTIMST Staff Nurse - 2016

Explanation

Myasthenia Gravis (MG) is an autoimmune disorder where the body's immune system mistakenly attacks and damages acetylcholine (ACh) receptors at the neuromuscular junction.
This damage reduces the number of available receptors for ACh, a neurotransmitter essential for muscle contraction.
The defining clinical sign is fatigability: muscles become progressively weaker with repeated use and recover strength after a period of rest.
This occurs because sustained activity depletes the available ACh, and the reduced number of receptors cannot maintain muscle activation, leading to reversible weakness.

Option A: MG is a disease of the neuromuscular junction, which is part of the motor system. It does not affect sensory nerves or pathways.
Option C: While MG commonly causes visual problems, it is due to weakness of the extraocular muscles (causing double vision or drooping eyelids), not a primary loss of visual acuity.
Option D: MG is a peripheral nervous system disorder. It does not affect the central nervous system (the brain and spinal cord), so cognitive functions like intelligence are preserved.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hallmark clinical feature of Myasthenia Gravis as background academic context rather than a clinical decision trigger.
Nurses must administer anticholinesterase medications (e.g., pyridostigmine) precisely on time, typically 30-60 minutes before meals, to maximize muscle strength for chewing and swallowing, thereby reducing the risk of aspiration.
Patient education is crucial and should focus on energy conservation. This includes planning demanding activities for the morning when strength is greatest and incorporating scheduled rest periods throughout the day.
A key nursing responsibility is monitoring for respiratory compromise, as weakness of the diaphragm and intercostal muscles can lead to respiratory failure. This is a medical emergency known as a myasthenic crisis.

How to Approach the Question

First, identify the core concept of the question: the most defining feature of Myasthenia Gravis (MG).
Recall the basic pathophysiology of MG. It's an autoimmune disease affecting the connection between nerves and muscles (neuromuscular junction).
Link the pathophysiology to the symptoms. The immune attack on acetylcholine receptors means that with repeated use, the muscle's ability to receive signals and contract fades.
Evaluate each option based on this core concept. 'Reversible fatiguability' perfectly describes the phenomenon of weakness with activity that improves with rest.
Eliminate the other options by remembering what MG is not. It is not a sensory disorder (ruling out impaired touch), not a disease of the eye's lens or retina (ruling out vision deterioration), and not a brain disorder (ruling out impaired intelligence).

Concept Tested & Keywords

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E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 1665-1667

E6 Medicine Davidson Principles Practice 24e p. 1161-1163