BPAG1 is the major antigenic determinant of autoimmune sera of bullous pemphigoid (BP) patients. It is made by stratified squamous epithelia, where it localizes to the inner surface of specialized integrin-mediated adherens junctions (hemidesmosomes). To explore the function of BPAG1 and its relation to BP, we targeted the removal of the BPAG1 gene in mice. Hemidesmosomes are otherwise normal, but they lack the inner plate and have no cytoskeleton attached. Though not affecting cell growth or substratum adhesion, this compromises mechanical integrity and influences migration. Unexpectedly, the mice also develop severe dystonia and sensory nerve degeneration typical of dystonia musculorum (dt/dt) mice. We show that in at least one other strain of dt/dt mice, BPAG1 gene is defective.