Medically important causes of Spider Angiomata

Spider Angiomata are tiny vascular lesions characterized by a central pulsating arteriole with radiating branches. The narrow vascular branches resemble the legs of a spider.

Spider angiomata is also called as a Spider Nevus, Spider Angioma, and Nevus Araneus. Up to 15% of the healthy population may have one or more spider angiomata.

What causes Spider Angiomata?

The exact cause of a spider angiomata is not known, however, the primary belief is that a high estrogen to androgen is the main factor causing spider angiomata.

Thus, female patient and especially those on estrogen containing oral contraceptives have a high tendency to develop spider angiomata.

Furthermore, since these are vascular lesions, they may disappear in patients with hypotension, after death, after discontinuing oral contraceptives and after menopause sets in.

Spider Nevi are not contagious

What happens when the centre of the spider angiomata is compressed?

Since the center o the lesion is an arteriole with smaller vessels branching out of it, pressure at the center will obliterate it. This will cut the blood supply of the branching vessels, leading to disappearance of the lesions.

spider angiomata
Spider angiomata. Note the central arteriole with branching vessels
spider angiomata
Disappearance of the spider angiomata after application of pressure on the center

Important Medical Conditions associated with Spider Angiomata ….

Up to 15% of the healthy population may have one or more Spider Nevi, However, these lesions should not be ignored if they are extensive, or are associated with other clinical features of the following diseases

Liver Diseases:

The liver is the major organ responsible for metabolizing hormones. In patients with liver disease, hormones especially estrogens cannot be metabolized.

Furthermore, the peripheral conversion of androstenedione and testosterone to the circulating estrogen is increased. Thus the ratio of testosterone to estradiol decreases and patients develop a hyperandrogenic state.

This is manifested by Spider nevi, gynecomastia, and palmar erythema. Patients should be investigated for a diseased liver and the underlying cause of the liver.

spider angiomata
palmar erythema in liver disease

These include Liver function tests (ALT, AST, Albumin, and Prothrombin time), hepatitis serology (hepatitis B and C serology), Ferritin, cerruloplasmin, ANA (antinuclear antibodies) and ASMA (antismooth muscle antibodies)


Just like liver disease, hyperthyroidism is associated with increased estrogens in the body. The conversion of androstenedione to estrone and estradiol, and testosterone to estrone is significantly increased in patients with hyperthyroidism.

Patients who have spider nevi along with any of the following features should be investigated for hyperthyroidism:

  1. Unintentional weight loss
  2. Goiter (Neck Swelling)
  3. Heat intolerance
  4. Palpitations
  5. Excessive seating, and
  6. hyper-defecation (increased frequency of bowel movements)

Investigations for hyperthyroidism include thyroid stimulating hormones, T3 and T4, neck ultrasound or a radio-iodine scan.

Oral contraceptive pills

Estrogen-containing oral contraceptive pills lead to an increase in the plasma estradiol levels. Thus, these medicines can directly lead to a hyper-estrogenic state resulting in spider nevi.

When estrogen containing Oral contraceptive pills are stopped, Spider nevi usually stop disappearing. It takes about nine months to twelve months for the lesions to disappear.

How to treat spider angiomata?

Spider Nevi usually do not require treatment. For cosmetic reasons, Laser therapy, elctrodessication and camouflauge have all been used. It is important to first look in to the underlying cause of the spider nevi and treat it accordingly.

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