Irregular in appearance, they are usually quite large, and caused by a deficiency or absence in the nerve supply to blood vessels. This causes vasodilation, the dilation of blood vessels, causing blood to pool or collect in the affected area. Over time, port-wine stains may become thick or develop small ridges or bumps, and do not fade with age. Such birthmarks may have emotional or social repercussions. Port-wine stains occur in 0.3% of the population, equally among males and females. They frequently express unilaterally, i.e., on only one side, not crossing the midline of the body. Often on the face, marks on the upper eyelid or forehead may be indicative of a condition called Sturge–Weber syndrome. Additionally, port-wine stains in these locations may be associated with glaucoma and seizures. Treatment
Most birthmarks are harmless and do not require treatment. Pigmented marks can resolve on their own over time in some cases. Vascular birthmarks may require reduction or removal for cosmetic reasons. Treatments include administering oral or injected steroids, dermatological lasers to reduce size and/or color, or dermatologic surgery. Historical Explanations
Many explanations were given to explain the origin of birthmarks. Occasionally, it was said that children could be marked or  imprinted upon by scares or frights given to the mother during the pregnancy.
Management
Management is dependent upon the severity, or degree, of the blockage, the consistency of symptoms, as well as the cause of the AV block.Patients with first-degree AV block do not have any resulting severe or life-threatening symptoms, such as symptomatic bradycardia or hypotension, and, thus, do not require treatment.Similarly, patients with second-degree Mobitz I AV block rarely develop life-threatening symptoms, and patients who are asymptomatic do not require treatment. However, in some cases, patients with Mobitz I block can develop life-threatening symptoms that require intervention. These patients often respond well to atropine, but may require temporary transcutaneous pacing or transvenous pacing until they are no longer symptomatic.Patients with second-degree Mobitz II and third-degree heart block are much more likely to have symptomatic bradycardia and hemodynamic instability, such as hypotension. Additionally, there is an increased risk of patients with Mobitz II heart block developing third-degree heart block. Therefore, these patients often require temporary pacing with transcutaneous or transvenous pacing wires, and many will ultimately require a permanent implanted pacemaker.If the heart block is found to be caused by a reversible condition, such as Lyme disease, the underlying condition should first be treated. Often, this will lead to resolution of the heart block and the associated symptoms. References
External links

Second-Degree Atrioventricular Block at eMedicine