Muscle specific tyrosine kinase (MuSK) is a surface membrane enzyme that plays an essential role in acetylcholine receptor (AChR) aggregation during neuromuscular junction (NMJ) development.
AChR antibodies are found in 85% of patients with generalised myasthenia gravis (MG) and antibodies to MuSK (mostly IgG4) are seen in around half of the AChR seronegative patients. MUSK antibodies are not found in ocular MG or in MG patients with AChR antibodies.
Distinguishing between AChR+ve MG and MuSK+ve MG is important for treatment decisions. MuSK+ve MG patients respond well to plasma exchange and Rituximab therapy but can have adverse effects from the standard AChR+ve MG therapy of acetylcholinesterase inhibitors and do not benefit from thymectomy or complement inhibitors (Sakano, S. et al. BMC Neurol 20, 240 (2020)).
Fatigueable muscle weakness
|Sample & container required
|Serum (rust top or yellow tube)
|5-10 mL blood (1 mL serum)
Not currently performed in house; this test is performed by radioimmunoassay at OUH Oxford Immunology Laboratory.