Pathogenesis of port wine stains. A new hypothesis.

Port wine stains have been shown to be lesions formed by the progressive dilatation of vessels within the superficial cutaneous vascular plexus. Previous investigators have been unable to define abnormalities of vessel structure or perivascular stromal tissues. We, however, have demonstrated morphologically that port wine stains are lacking proper innervation, and have shown them to behave differently than normal skin, physiologically. Dermal vessels are under the control of sympathetic nerves which course through the dermis and cause vasoconstriction without a parasympathetic system for counterregulation. We, therefore, propose that continued blood flow in the absence of tonic modulation is the basis for the vascular ectasia that characterizes the port wine stain.