What Caused Rash Of Blistery Irregular Bordered Spots Surrounding Neck?

What caused rash of blistery irregular bordered spots surrounding neck? It started in soft area on left side of lower neck then spread in a +one inch band across front and back of neck to right side my neck. Some scattered spots upper torso over several weeks, then cleared up --itching was very mild. Blistery surface of spots eventually sluffed off leaving brownish spots where blisters had been. Since then I'm experiencing weakness in my back and a mild stiffness in the left side of neck muscles...related? What?