Two entities can precede the clinical and biological signs of hepatitis B virus (HBV) infection: the various lesions of the serum sickness-like prodrome (urticaria, maculopapular exanthem, purpura, etc.) induced by the deposition of intravascular circulating immune complexes and papular acrodermatitis of childhood in which the physiopathological role of HBV has not yet been established. The persistence of HBs antigen (HBs Ag) may give rise to the purpuric lesions of essential mixed cryoglobulinemia and to the livedo, the nodules and ulcerations of poly-arteritis nodosa.