8049 – Anti-MuSK IFA

Intended Purpose

The Anti-MuSK IFA is an immunofluorescence assay (IFA) for the qualitative and semi-quantitative determination of IgG antibodies in human serum against muscle specific tyrosine kinase (MuSK) on HEp-2 cells. The Anti-MuSK IFA is intended as an aid in the diagnosis of myasthenia gravis (MG) in conjunction with other clinical and laboratory findings. This assay is particularly useful for detecting MuSK antibodies in patients who test negative for acetylcholine receptor antibodies, helping to identify a subset of MG patients with distinct clinical features. It supports differential diagnosis, guides appropriate treatment selection, and can provide information for monitoring disease progression and therapeutic response. The test is suitable for use in specialized laboratories by trained personnel. The immunoassay is designed for manual professional in vitro diagnostic use.

Diagnostic Relevance

Myasthenia gravis (MG) is a neurological autoimmune disease characterized by impaired signal transmission between nerves and muscles. It results from autoantibodies targeting structures of the post-synaptic membrane at the neuromuscular end-plate. The disease typically causes load-dependent weakening of skeletal muscles, which worsens during the day and improves with rest. In the majority of patients (about 85%), antibodies against acetylcholine receptors are detectable. In 1–10% of cases, antibodies against muscle-specific tyrosine kinase (MuSK) are present. Some patients show low-affinity acetylcholine receptor antibodies or antibodies against lipoprotein receptor-related protein 4 (LRP4). A small subset of patients likely has MG but shows no detectable antibodies, a condition known as seronegative myasthenia gravis. Detection of these autoantibodies is critical for diagnosis, guiding treatment, and understanding disease subtypes. Autoantibody testing helps differentiate MG from other neuromuscular disorders and is essential for clinical decision-making and patient management.