🧪 What is this Test?
The MuSK Antibody (MuSK Ab) Test detects anti-muscle-specific kinase (MuSK) antibodies in the blood. These antibodies are associated with Myasthenia Gravis (MG), a neuromuscular disorder that causes muscle weakness and fatigue.
📊 Normal Ranges:
✅ Negative: < 0.02 nmol/L (No detectable MuSK antibodies)
⚠️ Borderline: 0.02 – 0.05 nmol/L (May require further testing)
🚨 Positive: > 0.05 nmol/L (Indicates MuSK-positive Myasthenia Gravis)
🎯 Purpose of the Test:
✔️ Diagnose Myasthenia Gravis (MG), especially MuSK-positive MG
✔️ Differentiate between types of MG (AChR antibody-positive vs. MuSK-positive)
✔️ Confirm diagnosis when acetylcholine receptor (AChR) antibody tests are negative
✔️ Monitor disease progression and response to treatment
⚠️ Why Might You Need This Test?
Symptoms of Myasthenia Gravis, such as:
🔹 Muscle weakness (face, neck, limbs)
🔹 Drooping eyelids (ptosis)
🔹 Difficulty speaking, swallowing, or breathing
🔹 Fatigue that worsens with activity
Negative AChR antibody test but suspected MG
To guide treatment decisions for MG patients
📌 Understanding the Results:
Negative MuSK Ab (<0.02 nmol/L): MG is unlikely, but further testing may be needed
Positive MuSK Ab (>0.05 nmol/L): Confirms MuSK-positive MG, requiring medical management
Borderline MuSK Ab (0.02 – 0.05 nmol/L): May need repeat testing or additional diagnostic evaluation
🔬 Additional Notes:
MuSK-positive MG tends to cause more severe bulbar and respiratory symptoms than AChR-positive MG
Often tested along with Acetylcholine Receptor (AChR) Antibodies, Electromyography (EMG), and Tensilon Test
Early diagnosis and treatment can help manage symptoms and improve quality of life