AANP Family Nurse Practitioner (FNP) Certification ExamAssessmentMedium
A 42-year-old female presents with a 6-month history of fatigue, generalized muscle weakness, and difficulty climbing stairs. She also reports intermittent double vision and drooping eyelids, which worsen with activity and improve with rest. Physical examination reveals bilateral ptosis and mild proximal muscle weakness. Which of the following diagnostic tests is most likely to confirm the suspected diagnosis?
- AThyroid stimulating hormone (TSH) and free T4.
- BAnti-acetylcholine receptor (AChR) antibody test.
- CElectromyography (EMG) with nerve conduction studies (NCS).
- DSerum creatine kinase (CK) level.
Show answer & explanationAnswer & explanation
Correct answer: B. Anti-acetylcholine receptor (AChR) antibody test.
The patient's symptoms of fluctuating muscle weakness, ptosis, double vision (diplopia) that worsens with activity and improves with rest are classic for Myasthenia Gravis (MG). MG is an autoimmune disorder characterized by antibodies against acetylcholine receptors at the neuromuscular junction. The anti-AChR antibody test is highly specific and often diagnostic for MG.
Why the other options are wrong
- A. While thyroid dysfunction can cause fatigue and muscle weakness, the specific pattern of fluctuating ptosis and diplopia worsening with activity points more strongly to MG.
- C. EMG with NCS can show a decremental response with repetitive nerve stimulation, which supports MG, but the antibody test is more specific for diagnosis.
- D. Serum CK levels are typically normal in Myasthenia Gravis, as it is a disorder of the neuromuscular junction, not muscle breakdown.
Myasthenia Gravis Diagnosis
Myasthenia Gravis (MG) is an autoimmune neuromuscular disorder characterized by fluctuating muscle weakness that worsens with activity and improves with rest, caused by antibodies against AChR.
- Hallmark symptoms: ptosis, diplopia, generalized weakness.
- Symptoms worsen with exertion, improve with rest.
- Anti-AChR antibody test is highly specific for diagnosis.
Memory trick: MG: Antibodies Attack, Muscles Slack