- Myasthenia Gravis and Muscle-specific Tyrosine Kinase Antibodies (MuSK Ab)
- MuSK Ab Testing
- Technical Information
*Download the requisition onto a computer and open with Adobe Acrobat/Reader for a writeable PDF
Myasthenia Gravis and Muscle-specific Tyrosine Kinase Antibodies
Myasthenia gravis (MG) is the prototypical antibody-mediated autoimmune disease, with antibodies (Ab) directed against components of the neuromuscular junction, and it is the most common disorder of neurotransmission. In about 85% of generalized MG patients, antibodies directed against the acetylcholine receptor (AChR) are detected. Among the remaining 15% of patients, a variable proportion have antibodies against the extracellular domain of muscle-specific tyrosine kinase (MuSK), a 110 kD transmembrane protein which, together with agrin, low density lipoprotein receptor-related protein 4 (LRP4), and rapsyn, is involved in the clustering of AChR. MuSK Abs have been reported worldwide in AChR Ab-negative patients with frequencies ranging from 0-64%, depending on the ethnic group or geographic location. Among the double-negative MG patients, without anti-AChR or -MuSK antibodies, some have antibodies against LRP4 and others to agrin.
Clinically, MG is characterized by muscle weakness and fatiguability, affecting mainly ocular muscles in AChR MG, resulting in ptosis and diplopia. On the other hand, MuSK MG is characterized by a more severe disease, more frequent myasthenic crises, prominent bulbar features and refractory response to thymectomy, whilst the clinical phenotype of double-negative MG is not well defined.
MuSK Ab Testing at the Neuro-Immunology Lab
The MuSK antibody assay uses surface plasmon resonance (SPR) technology (Biacore 3000) to determine and quantify the presence of anti-MuSK antibodies in patients’ serum utilizing MuSK protein that is immobilized onto a gold chip.
MuSK Ab testing may only be requested by neurologists, ophthalmologists neuro-ophthalmologists. Please note that only samples negative for acetylcholine receptor antibodies will go on to be tested for MuSK Ab.
The test is run monthly or more frequently, if the number of samples we receive warrants it.
Serum samples should be collected in SST tubes, clotted for a minimum of 30 minutes, centrifuged at 4°C, transferred to cryovials, and stored at 4°C prior to shipping.
Two (2) to five (5) ml of serum should be shipped according to IATA, ICAO and Canadian transportation goods regulation. Samples do not need to be frozen. Please courier your samples together with a completely filled out requisition (see “Lab Requisition” above). When applicable, the clinical information should be filled out by the referring physician (whom we will call or write in case of discrepant results).
Results will be faxed (please include a fax number on the requisition).
Ship samples to:
University of British Columbia Hospital
Room S-157, 2211 Wesbrook Mall
Vancouver, B.C, Canada
For all other inquiries, please contact us:
Lab Phone: (604) 822-7175
Office Phone: (604) 822-7696
Fax: (604) 822-0758