Port-wine stain. This unilateral vascular malformation has a markedly different histology, significance, and natural history from that of the salmon patch. The port-wine stain is made up of capillary ectasias that may be present throughout the dermis and that gradually increase with age. The color changes from pink to purple as the patient grows, and the lesions may become nodular during adult life. Because port-wine stains show no tendency to involute, they may represent a significant, lifelong cosmetic problem.
Rocky Mountain spotted fever. This disease is caused by Rickettsia rickettsii and is transmitted by a number of different ticks. Despite its geographical title, Rocky Mountain spotted fever is present in many locations throughout the United States and the entire Western Hemisphere. After infection by tick bite, there is an incubation period of 2–14 days. The abrupt onset of the disease includes severe headache, fever, chills, arthralgia, and myalgia. After 2–3 days of these constitutional symptoms, erythematous macules erupt on the wrists, hands, forearms,legs, and ankles, as seen in these figures. Lesions then spread to the palms and soles and the trunk. The macules originally blanch with pressure but soon become purpuric and even necrotic. The disease causes a severe vasculitis and complications include disseminated intravascular coagulation, hemorrhage into the gastrointestinal and urinary tracts, and cardiovascular collapse.