MUSK and pemphigus: For example, antibodies to MuSK interrupt a signal transduction pathway required for the functioning of the neuromuscular junction, therefore causing muscle weakness in patients with MuSK-MG (62, 63), antibodies against desmoglein 1 and/or 3 lead to loss of cell adhesion between keratinocytes, therefore causing blistering of the skin in pemphigus patients (65, 68, 69), and inhibitory antibodies against the protease ADAMTS13 lead to an accumulation of multimeric von Willebrand factor and vascular occlusion in patients with TTP (70–72).