Synonyms: naevus araneus, naevus arachnoidius, spider angioma, tache stellaire, étoile vasculaire.

Spider naevi is the name given to small angiomata which appear on the surface of the skin. They were first described in 1869 by the English physician Erasmus Wilson¹ who noted them on the skin of a publican. They are described as "spiders" due to their appearance - the central, ascending vessel resembling the body of a spider, with the finer radiating vessels looking like the legs of a spider.

Epidemiology:

• 15-20% of healthy individuals will have one or more spider naevi
• Multiple spider naevi are more indicative of underlying disease
• They are common in childhood and show an equal sex incidence
• Spider naevi may also develop in pregnancy, or when taking the oral contraceptive pill
• Just one, or a few spiders, are more common in women
• There is probably no racial difference in prevalence but they are less obvious on darker skin

Presentation

Spider naevi are usually asymptomatic. Presentation is because of cosmetic effect, especially if they are on the face or there is possibly concern about the aetiology. They may rarely bleed with minor trauma.

They are small lesions with a number of tiny blood vessels radiating from them to resemble the legs of a spider. The centre is about 1 mm in diameter and the whole lesion about 5 to 10 mm across. Firm pressure with something small such as the end, not the nib, of a ball point pen, will cause it to blanch and when the pressure is released it will rapidly refill.

Lesions most frequently occur on the face, below the eyes, and over the cheekbones. Other common sites include the hands, forearms and ears. Spider naevi may occur on the trunk, or on the scalp, neck, arms and hands. Almost all spider naevi occur on the upper part of the body and only 1% below the umbilicus. Traditional teaching is that they are restricted to areas drained by the superior vena cava but this is disputed by William Bean, one of the great founders of hepatology.⁴ Although healthy individuals may have one or more lesions, the presence of large numbers suggests underlying disease. Look for other stigmata of liver disease.

Ask about drugs, as these may cause liver damage. Ask about alcohol consumption.

Differential diagnosis

Spider naevi may be differentiated from other lesions with a similar appearance by the fact that they blanch with pressure, and refill again from the centre outwards:

• Campbell de Morgan spots are bigger, red spots without vessels radiating and they tend to occur in older people
• Insect bites may have a central punctum and should soon resolve. They may itch.
• Telangiectasia are dilated small blood vessels. Osler-Rendu-Weber syndrome is a condition in which multiple telangiectasia occur.
• Haemangioma is a larger red spot, often raised

Investigations

For most healthy young people with a single or just a few lesions, and especially children, no investigation is required.
Otherwise, assess liver function. Thyroid function tests may also be indicated as they can occur with thyrotoxicosis.

Associated conditions

Spider naevi may be associated with any condition that results in increased circulating levels of oestrogen including:

• Pregnancy
• Alcoholic cirrhosis
• Hepatitic cirrhosis
• Hepato-pulmonary syndrome

Management

Usually no treatment is required and many will fade spontaneously or resolve as the underlying condition improves. Spider naevi may be treated with laser therapy⁵ or electrodessication if desired for cosmetic reasons.

Prognosis

Benign lesions tend to resolve spontaneously but may take a number of years to do so. If associated with pregnancy they tend to go about 6 or 7 months after delivery. They will also resolve some time after stopping oral contraceptives. If associated with liver disease, they may resolve if the liver disease improves.

Epilogue

Although Erasmus Wilson made the classic description of spider naevi, it was William Bean who studied them extensively and who noted the association with cirrhosis, especially of the alcoholic kind. He will also be remembered for his poetry on the subject of alcoholic cirrhosis, spider naevi and palmar erythema and it is worthy of repetition:⁶

An older Miss Muffett
Decided to rough it
And lived upon whisky and gin.
Red hands and a spider
Developed outside her for
Such are the wages of sin.