AANP Family Nurse Practitioner (FNP) Certification ExamAssessmentMedium
A 45-year-old female presents with a 6-month history of progressive fatigue, generalized weakness, and ptosis that worsens throughout the day and improves with rest. She also reports occasional difficulty swallowing and chewing. Neurological examination reveals fluctuating muscle weakness. Which of the following diagnostic tests should the FNP order first to confirm the suspected diagnosis?
- AAnti-acetylcholine receptor (AChR) antibody test
- BBrain MRI
- CElectromyography (EMG) with repetitive nerve stimulation
- DThyroid stimulating hormone (TSH)
Show answer & explanationAnswer & explanation
Correct answer: A. Anti-acetylcholine receptor (AChR) antibody test
The patient's symptoms of fluctuating muscle weakness, ptosis, and difficulty swallowing/chewing, all worsening with activity and improving with rest, are classic for Myasthenia Gravis. The anti-AChR antibody test is highly specific and sensitive for this condition and is typically the first-line diagnostic test.
Why the other options are wrong
- B. A brain MRI would be used to rule out central nervous system disorders, which is less likely given the specific fluctuating muscle weakness pattern.
- C. EMG with repetitive nerve stimulation is a supportive diagnostic test, but the antibody test is usually performed first.
- D. TSH would be used to rule out hypothyroidism, which can cause fatigue, but not the specific fluctuating weakness and ptosis pattern seen here.
Myasthenia Gravis Diagnosis
Myasthenia Gravis is an autoimmune disorder characterized by fluctuating muscle weakness and fatigue, especially in muscles controlling eyes, face, throat, and limbs. Symptoms worsen with activity and improve with rest.
- Caused by antibodies blocking or destroying acetylcholine receptors at the neuromuscular junction.
- Common initial symptoms include ptosis and diplopia.
- Diagnosis often involves clinical presentation, anti-AChR antibody test, and EMG.
Memory trick: Myasthenia: Muscles Melt, Eyes droop, Swallowing Slows, All Day Long, then Rest Revives.