Myasthenia gravis (MG) is a chronic autoimmune disease affecting muscles function. Within neuromuscular junctions, the immune system attacks the nicotinic acetylcholine receptors of muscle cells, leading to impaired synaptic transmission and, consequently, a reduced muscle activation. In contrast to primary MG diagnosis, reliable tools for assessment of MG disease activity in clinical routine, e.g. for therapy adjustments, are still an unmet and urging medical need.

The invention aims at monitoring inter-alpha-trypsin inhibitor heavy chain H3 (ITIH3) levels from serum of MG patients. ITIH3 is a robust biomarker allowing a reliable prediction of MG`s disease activity feasible in daily clinical routine. Monitoring can easily be made by quantitative ELISA in routine blood collection. This approach provides objective results, excluding time-of-day dynamics and subjective symptom burden of patients or examiners. Especially with the very recent advent of the development of new therapeutic strategies, ITIH3 as biomarker indicating MG disease activity and identifying patients at risk for disease deterioration represents a meaningful invention in the field.