Physical Therapy Assistant Practice Exam

Which disease is characterized by fluctuating weakness and fatigue of skeletal muscles?

1. Multiple sclerosis

2. Huntington's disease

3. Guillain-Barre syndrome

4. Myasthenia gravis

The correct answer is: Myasthenia gravis

The disease characterized by fluctuating weakness and fatigue of skeletal muscles is myasthenia gravis. This condition results from an autoimmune response in which antibodies attack the nicotinic acetylcholine receptors at the neuromuscular junction. This impairment leads to weak and fatigued skeletal muscles, particularly after periods of activity, with symptoms often improving after rest. Individuals with myasthenia gravis may experience muscle weakness that varies in intensity throughout the day, contributing to notable fluctuations in muscle strength. In contrast, the other diseases mentioned have different characteristics. Multiple sclerosis often involves central nervous system lesions leading to a range of neurological symptoms but does not primarily cause fluctuating weakness in the same way. Huntington's disease is a genetic disorder that primarily affects movement and cognitive function over time, and while muscle coordination is affected, it does not fluctuate in the same manner as myasthenia gravis. Guillain-Barre syndrome is characterized by rapid-onset muscle weakness due to autoimmune destruction of the peripheral nervous system, but it typically manifests more suddenly and does not involve the same kind of muscle fatigue fluctuations caused by an autoimmune attack on the neuromuscular junction.