What Is Cutaneous Mastocytosis?

Cutaneous mastocytosis is one of two types of mastocytosis, a rare disorder in which too many mast cells — a type of white blood cell that helps the immune system function properly — accumulate in the body.

In cutaneous mastocytosis, mast cells build up in the skin, causing skin changes or lesions, while in systemic mastocytosis, mast cells multiply abnormally in the bone marrow, digestive tract, liver, spleen, or other organs.

Maculopapular Cutaneous Mastocytosis/Urticaria Pigmentosa

This is the most common form of cutaneous mastocytosis and looks like small reddish-brown or brown spots on the skin that can be flat or elevated. At first, these may be mistaken for freckles. Plaque-like lesions — lesions greater than 1 centimeter in size — can also occur.

The bumps can be classified into two types, monomorphic (all spots look similar) and polymorphic (the spots vary in appearance).

Cutaneous Mastocytoma

Usually present at birth, cutaneous mastocytoma involves an isolated mastocytoma (mast cell tumor) that’s about 2 to 5 centimeters in diameter. It usually goes away on its own, but it can be surgically removed if needed. Four cutaneous mastocytomas or more may become a diagnosis of maculopapular cutaneous mastocytosis.

Diffuse Cutaneous Mastocytosis (DCM)

Cutaneous mastocytosis can cause a variety of symptoms, both on the skin and in other systems of the body.

Skin Symptoms

• Itchy or Inflamed Skin The skin can develop red, itchy patches or hives, or other changes, as described above.
• Rashes Maculopapular cutaneous mastocytosis often results in dark spots or bumps that may itch or swell when scratched.
• Flushing Some people experience redness or flushing of the skin, especially after exposure to heat, eating certain foods, or stress.
• Blistering In more severe cases, especially in diffuse cutaneous mastocytosis, the skin may blister and become painful. This only happens in babies and young children.

Systemic Symptoms

Even though mast cell overaccumulation occurs only in the skin in cutaneous mastocytosis, it can cause symptoms in other parts of the body, particularly the gastrointestinal system.

• Diarrhea
• Abdominal pain
• Peptic ulcers

• Diarrhea
• Gastrointestinal bleeding
• Decreased blood pressure

Risk factors for cutaneous mastocytosis include:

• Age Cutaneous mastocytosis most commonly appears in childhood, often before the age of 2.
• Environmental Triggers External factors like temperature changes, stress, infections, and certain medications may trigger symptoms.

Depending on the age of the person and the suspected type of cutaneous mastocytosis, diagnosis may involve a combination of the following:

• Physical Exam The skin will be examined to check for characteristic lesions like urticaria pigmentosa.
• Darier’s Sign If maculopapular cutaneous mastocytosis/urticaria pigmentosa lesions are found, the provider may lightly rub or scratch a small area of the affected skin. The development of redness or hives over or around the lesion within about five minutes is called Darier’s sign and suggests the presence of mast cells within the lesion.

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• Skin Biopsy A small sample of skin may be taken and examined under a microscope to confirm the presence of excessive mast cells.
• Blood Tests Measuring the levels of tryptase, a protein released by mast cells, can help confirm the diagnosis, though it's primarily used to assess systemic mastocytosis.
• Genetic Tests In some cases, additional tests, such as genetic testing, may be used to check for mutations in the KIT gene.

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• Bone Marrow Biopsy In adults, this may be used to look for unusual numbers of mast cells in the bone marrow. Because pediatric mastocytosis is usually limited to the skin and spontaneously improves as children get older, most infants and children don’t have to have a bone marrow biopsy performed.

While there is no cure for cutaneous mastocytosis, there are treatments available to manage symptoms and improve quality of life.

Epinephrine for Anaphylaxis

Although the risk of anaphylaxis is small compared to people with systemic mastocytosis, people with cutaneous mastocytosis (or their caregivers) should have at least two doses of epinephrine in self-injectable form or nasal spray available at all times.

Medication Options

• Antihistamines These are the mainstays of treatment to control symptoms like itching, flushing, and rashes.
• Cromolyn Sodium This medication can help stabilize mast cells, preventing the release of histamine and other chemicals. It can help with gastrointestinal symptoms.
• Leukotriene Modifiers These drugs help control symptoms like itching and abdominal discomfort when antihistamines alone aren’t enough.
• Proton Pump Inhibitors These drugs are helpful for treating stomach acid issues.
• Steroids Systemic glucocorticoids may be used for severe symptoms, but they aren’t recommended for routine or maintenance management. Short-term use of topical steroids may help reduce inflammation and itching in some patients.

Surgery

Phototherapy

Although prevention of cutaneous mastocytosis isn’t possible, there are ways to limit exposure to factors that can activate mastocytosis symptoms or trigger an anaphylactic reaction.

Avoiding Triggers

• Friction on the skin caused by touching or rubbing
• Being stung or bit by an insect, especially ants, wasps, and bees
• Alcohol
• Heat and humidity
• Physical exertion and stress
• Spicy foods, alcohol, and certain medications

Dietary Changes

Current guidelines don’t recommend a specific diet, but identifying food triggers can help manage symptoms or allergic reactions.

Foods that are more reactive include monosodium glutamate (MSG), alcohol, shellfish, artificial food dyes and flavorings, preservatives, pineapples, tomatoes and tomato-based products, and chocolate. However, these foods might not be an issue for everyone, and some people may have problems with other foods.

Overall, the prognosis for all types of cutaneous mastocytosis is excellent for children who experience the onset of skin lesions within the first two years of life, because it usually goes away.

The Mast Cell Disease Society

This advocacy group offers online and Facebook-based support groups and an online forum. It also has an online physician finder and a variety of downloadable reference guides for patients.

• Cutaneous mastocytosis is a rare condition in which abnormal mast cells accumulate in the skin, causing symptoms like rashes, itching, and flushing.
• It primarily affects infants and young children, though it can develop in adults.
• Medical treatments and lifestyle changes won’t cure the disease, but they can help manage symptoms.