Sunday, August 2

Nevus araneus - Spider nevus

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Nevus araneus (also known as spider angioma, vascular spider and spider telangiectasia) is a common benign, asymptomatic, vascular lesion appearing on the surface of the skin.
It was first described in 1867 by Erasmus Wilson, an English physician. It is present in nearly 10 to 15% of healthy adults and children. The term "Araneus" denotes a genus of orb-weaving spiders.

Nevus araneus occurs as a result of the dilation of the preexisting blood vessels. Araneus lesion consists of a central ascending arteriole from which numerous small vessels radiate. The central arteriole resembles a spider's body and the radiating vessels appear like spider legs. These lesions range in size from being just visible to 10mm in diameter.

Vascular spider lesions are commonly found in the distribution of the superior vena cava, occurring on the face, below the eyes, over the cheekbones, neck, upper trunk and arms. The nevus araneus association to the superior vena cava is disputed by some researchers. Children may have them also on their fingers and hands. Vascular spider is more common in women than in men, probably due to pregnancy and oral contraceptive use related occurrences.
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Pathophysiology and causes

The dilation of the preexisting dermal blood vessels is the primary cause of the appearance of these nevus araneus lesions. The vascular dilation is mostly idiopathic and is caused by the failure of the sphincteric muscle surrounding an arteriole. Compressing the central arteriole with a pinhead causes temporary obliteration of the telangiectasia. Releasing the pressure causes rush of blood from the central arteriole to the branching dilated blood vessels. Occasionally the arteriole may be observed to pulsate. Punctured arteriole may bleed profusely.

Araneus vascular malformations are normally unrelated to systemic diseases and health conditions. However, in a few cases, they have been associated with hyperthyroidism and thyrotoxicosis. High levels of circulating estrogen is another cause of araneus lesions, as in the case of pregnancy or during the use of oral contraceptives. The condition resolves in a few months after giving birth or after stopping oral contraceptive pills.

Nevus araneus is also associated with liver ailments such as chronic liver disease, hepatic failure, liver cirrhosis, hepatopulmonary syndrome and hepatic fibrosis. The appearance of numerous, large lesions in atypical locations is one of the strong clinical pointers to liver disease and alcohol abuse related severe liver dysfunction.

Vedamurthy M. et al. reported a case of a 36 year-old, non-alcoholic man with multiple, erythematous, asymptomatic macules distributed mainly on the chest. Earlier, the condition was diagnosed as an allergic reaction and antihistamines were prescribed. Six months later, the patient developed jaundice and diagnosed to have chronic liver disease. Dermatological examination revealed the presence of numerous spider nevi on the chest and abdomen. The researchers concluded that, "it would be advisable to screen the patients with spider nevi for liver disease as early detection could prove to be beneficial to the patient".

These nevus araneus lesions are probably due to the diseased liver being unable to optimally metabolize circulating estrogens. The elevated levels of estradiol/free testosterone ratio, serum vascular growth factors and substance P are other causes attributed to cause these lesions.

Nevus araneus symptoms

Nevus araneus appears like a spider, with a central, small, red papule surrounded by several radiating blood vessels. Pressure on the lesion causes temporary obliteration. When the pressure is removed, the lesion refills from the center to the radiating vessels. Occasionally the central arteriole is observed to pulsate. Normally, vascular spider appears on the upper half of the body.

Spider nevus diagnosis

Diagnosis of vascular spider is usually by clinical observation and by observing the classic refill pattern from the central arteriole to the radiating blood vessels. Blanching and temporary obliteration of the nevus araneus lesion on pressure is another indicator. Araneus malformations may have to be differentiated from telangiectatic mats (lacking central arteriole), varicose Veins, hemangioma, Campbell de Morgan spots, Osler-Rendu-Weber syndrome, telangiectasia with different etiologies and insect bites.

Nevus araneus treatment

For benign, idiopathic, nevus araneus, treatment usually is not necessary. Some lesions resolve rapidly while some may regress over the course of several years. Some vascular lesions may be permanent. In pregnant women, the vascular malformations caused by circulating hormones may resolve in a few months after childbirth. Those on oral contraceptives or hormonal supplementation may find spider nevus resolution after discontinuing the medications. Liver disease connected lesions may regress upon treatment of the ailment or after liver transplantation.
image of spider nevus
image of nevus araneus
Nevus araneus image source: https://commons.wikimedia.org/wiki/File:Spider_nevus.jpg
http://cnx.org/content/m14900/latest/
Image authors: Herbert L. Fred, MD and Hendrik A. van Dijk | License: (CC-BY 2.0)
Persistent, bothersome or cosmetically disfiguring nevus araneus may be treated by electrodesiccation or laser treatment. The central arteriole is completely electrodesiccated. Incompletely destroyed arteriole may lead to recurrence of spider nevus. Excessive desiccation may cause permanent scar formation. The KTP 532-nm laser treatment demonstrated a high success rate of nevus araneus clearance.
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References:
1.Khasnis A, Gokula R M. Spider nevus. J Postgrad Med 2002;48:307.
2.T. Enta. Nevus araneus (spider telangiectasia). Can Fam Physician. 1994 Jun; 40: 1105–1112.
3.Vedamurthy M, Vedamurthy A. Spider nevi: A presenting feature of chronic liver disease. Indian J Dermatol Venereol Leprol 2008;74:397-8.
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