THE TEST IS HIGHLY SPECIFIC AND SENSITIVE FOR THE DIAGNOSIS OF MYASTHENIA GRAVIS (MG), AN AUTOIMMUNE DISORDER THAT CAUSES MUSCLE WEAKNESS AND FATIGUE. A POSITIVE RESULT STRONGLY SUPPORTS THE DIAGNOSIS OF MG. THE LEVEL OF THE ANTIBODY MAY ALSO BE USED TO MONITOR THE EFFECTIVENESS OF TREATMENT.

MUSK ANTIBODIES HAVE BEEN DETECTED IN PATIENTS WITH MYASTHENIA GRAVIS WHO ARE SERONEGATIVE FOR ACETYLCHOLINE RECEPTOR (ACHR) ANTIBODIES. ANTIBODIES TO MUSK ARE PRESENT IN 40% OF ACHR ANTIBODY NEGATIVE PATIENTS. THIS ASSAY IS USED TO EVALUATE PATIENT RESPONSE TO THERAPIES FOR ONGOING MANAGEMENT.

AUTOANTIBODIES DIRECTED AGAINST CONTRACTILE ELEMENTS OF STRIATED MUSCLE ARE FOUND IN 30% ADULT PATIENTS WITH MYASTHENIA GRAVIS (MG) AND 80% CASES OF THYMOMA IN ASSOCIATION WITH MG. THE ANTIBODIES MAY ALSO BE DETECTED IN LAMBERT - EATON MYASTHENIC SYNDROME (5%), SMALL CELL LUNG CARCINOMA (5%), BREAST CARCINOMA, AUTOIMMUNE LIVER DISORDERS AND PATIENTS ON D-PENICILLAMINE (25%).