Definition
A Spider naevus, also called Spider nevus or Naevus araneus, is a skin sign that occurs in chronic liver diseases. The name is derived from the English word for spider, “spider”, and “naevus” for birthmark. A Spider naevus is a visible dilation of arterial vessels and can be several centimeters in diameter. The shape is star-shaped or spider-shaped, hence the name Spider naevus. The nevi are often found on the face, forehead, neck and chest wall.
Causes
Spider naevi develop in connection with various chronic liver diseases. The chronic connective tissue disease scleroderma or CREST syndrome, a special form of scleroderma, can also lead to the formation of spider naevi. The benign changes can occur in childhood and in pregnant women.
If they develop during pregnancy, they usually regress after delivery. In addition, above-average exposure to sunlight (UV radiation) can promote the development of a spider nevus. All in all, it can be seen that the development of a spider nevus can have different causes. In most cases, these are benign changes in the arterial blood vessels of the skin.
Origin
While there are clear causes in connection with the formation of spider naevi, the exact origin of the marks is not yet clear. One possible hypothesis is a local lack of oxygen, which promotes the release of growth factors. The released growth factors lead to increased vascular growth and the formation of spider naevi.
Where do Spider Naevi perform?
Spider naevi mainly occur in skin areas that are exposed to light. The face, forehead and neck are particularly often affected. In addition, the changes also occur in the area of the rib cage, i.e. the upper trunk, and on the arms and hands.
Diagnosis
Typically, a spidernaevus is diagnosed by a gaze diagnosis. The spider nevus has a characteristic star-shaped appearance. The attending physician will discuss with the patient the course of nevus formation over time and other possible symptoms.
A detailed examination of the nevus is performed with a magnifying glass and a physical examination with palpation and listening of the abdominal organs. As a rule, a blood sample is taken and the liver and hormone values are checked. Depending on the suspected diagnosis of a possible liver disease or other cause, a referral to a specialist can be made.