Angiokeratoma is a condition in which small, dark spots appear on the skin. Most of the time, they do not need treatment, but they can sometimes be a symptom of an underlying condition.

They can appear anywhere on your body. These lesions happen when tiny blood vessels called capillaries dilate, or widen, near the surface of your skin.

Angiokeratomas may feel rough to the touch. They often appear in clusters on skin around the:

  • penis
  • scrotum
  • vulva
  • labia majora

They can be mistaken for a rash, skin cancer, or a condition like genital warts or herpes. Most of the time, angiokeratomas are harmless and don’t need to be treated.

Angiokeratomas can sometimes be a symptom of an underlying condition, such as the rare genetic disorder known as Fabry disease (FD). You may need to see a doctor for treatment to prevent complications.

Types of angiokeratoma include:

  • Solitary angiokeratoma. These often appear alone. They’re often found on your arms and legs. They aren’t harmful.
  • Angiokeratoma of Fordyce. These appear on the skin of the scrotum or vulva. They’re most commonly found on the scrotum in large clusters. This type can develop on the vulva of pregnant women. They’re not harmful, but are prone to bleed if they’re scratched.
  • Angiokeratoma of Mibelli. These result from dilated blood vessels that are closest to the epidermis, or the top layer of your skin. They’re not harmful. This type tends to thicken and harden over time in a process known as hyperkeratosis.
  • Angiokeratoma circumscriptum. This is a much rarer form that appears in clusters on your legs or torso. You can be born with this type. It tends to morph in appearance over time, becoming darker or taking different shapes.
  • Angiokeratoma corporis diffusum. This type is a symptom of FD. It can happen with other lysosomal disorders, which affect how cells function. These conditions are rare and have other noticeable symptoms, such as burning of the hands and feet or vision problems. These angiokeratomas are most common around the lower body. They can appear anywhere from the bottom of your torso to your upper thighs.

The exact shape, size, and color can vary. You can also have additional symptoms if you have an associated condition, such as FD.

In general, angiokeratomas display the following symptoms:

  • appear as small- to medium-sized bumps from 1 millimeter (mm) to 5 mm or in jagged, wart-like patterns
  • have a dome-like shape
  • feel thick or hard on the surface
  • show up alone or in clusters of only a few to nearly a hundred
  • are dark-colored, including red, blue, purple, or black

Angiokeratomas that have just appeared tend to be reddish in color. Spots that have been on your skin for a while are usually darker.

Angiokeratomas on the scrotum may also appear along with redness across a large area of the scrotum. Angiokeratomas on the scrotum or vulva may also bleed more easily when scratched than those on other parts of your body.

If you have a condition like FD that’s causing angiokeratomas to appear, other symptoms you might experience include:

  • acroparesthesias, or pain in your hands and feet
  • tinnitus, or ringing sound in your ears
  • corneal opacity, or cloudiness in your vision
  • hypohidrosis, or not being able to sweat properly
  • pain in your stomach and bowels
  • feeling the urge to defecate after a meal

Angiokeratomas are caused by the dilation of blood vessels close to the surface of the skin. Solitary angiokeratomas are likely caused by injuries that previously happened in an area where they appear.

FD is passed down in families, and can cause angiokeratomas. About 1 in every 40,000 to 60,000 men have FD, according to the U.S. National Library of Medicine’s genetics department.

Other than their association with FD and other lysosomal conditions, it’s not always clear what the underlying cause of angiokeratomas. Possible causes include:

Angiokeratomas are typically harmless. You don’t always need to see a doctor for a diagnosis.

But if you notice other symptoms, like frequent bleeding or symptoms of FD, see your doctor right away for a diagnosis and treatment. You may also want to see your doctor if you suspect that a spot that looks like an angiokeratoma might be cancerous.

Your doctor will take a tissue sample of an angiokeratoma to diagnose it. This is known as a biopsy. During this process, your doctor may excise, or cut out, an angiokeratoma from your skin in order to remove it for analysis. This may involve your doctor using a scalpel to remove the angiokeratoma from its base underneath the skin.

Your doctor may also recommend a GLA gene test to see if you have FD. FD is caused by mutations in this gene.

Angiokeratomas generally doesn’t need to be treated if you aren’t experiencing any discomfort or pain. You may want them removed if they frequently bleed or for cosmetic reasons. In this case, several treatment options are available:

  • Electrodessication and curettage (ED&C). Your doctor numbs the area around the angiokeratomas with local anesthesia, then uses electric cautery and tools to scrape the spots off and remove tissue.
  • Laser removal. Your doctor uses lasers, such as a pulsed dye laser, to destroy dilated blood vessels that cause angiokeratomas.
  • Cryotherapy. Your doctor freezes the angiokeratomas and surrounding tissues and removes them.

Treatment for FD may include medications, such as:

  • Agalsidase beta (Fabrazyme). You’ll receive regular Fabrazyme injections to assist your body in breaking down extra cell fat that’s built up due to missing an enzyme caused by GLA gene mutations.
  • Neurontin (Gabapentin) or carbamazepine (Tegretol). These medications can treat hand and foot pain.

Your doctor may also recommend that you see specialists for heart, kidney, or nervous system symptoms of FD, too.

Angiokeratomas aren’t usually cause for concern. See your doctor if you notice any bleeding or injury to the angiokeratomas, or if you suspect that there’s an underlying condition causing you discomfort or pain.