Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 29, 2016

Mastocytosis is a rare disorder characterized by the presence of an overabundance of mast cells within the body. This disease may present itself in its cutaneous form or systemic form, depending upon which tissues are affected. Mastocytosis affects less than 200,000 people in the United States and can be found equally among children and adults.


Definition & Facts

Mast cells serve as an alarm system to alert the immune system that help is needed somewhere in the body. Mast cells release histamines and cytokines to indicate that disease is present within the tissue. These cells are typically found in the skin, lymph nodes, and internal organs. They can also be found in the lining of the lungs, intestines, and stomach

Mastocytosis can manifest in two forms. Cutaneous form, also known as urticaria pigmentosa, is the most common form. This type occurs when too many mast cells infiltrate the skin and it is most commonly found among infants and children.

The second form, systemic mastocytosis, occurs when there is an abnormally high concentration of mast cells within internal organs. This type is more commonly seen in adults, affecting the liver, spleen, bone marrow, and small intestine. The increased amount of mast cells within the tissue leads to abnormal reactions by the body similar to allergic reactions that disrupt normal body functions.

Symptoms & Complaints

Symptoms of mastocytosis vary depending on the tissues involved. The most visible symptoms are those involving the skin. Patients usually notice red, pink or yellow bumps on the skin that itch, swell, and sometimes blister when rubbed or scratched.

In many patients, itchy brown patches are present on the skin. Flushing and overall itching are often present, as well as more severe allergic reaction symptoms including low blood pressure (hypotension), faintness, and anaphylaxis.

Cases involving internal organs manifest themselves in symptoms including abdominal pain, cramping, bloating, nausea, and vomiting. These symptoms often are accompanied by pain in the bones and pain in the muscles, headaches, wheezing, and dizziness.

Over time, ulcers and lesions may develop in the stomach, and the liver and spleen may become enlarged (hepatomegaly and splenomegaly). These complications may cause malabsorption, anemia, and a reduced blood platelet count (thrombocytopenia).


The exact cause of mastocytosis is unknown. Research has shown an association between mastocytosis and a genetic mutation affecting the KIT gene. This mutation causes mast cells to be more sensitive to the effect of SCF, which is the stem cell factor that acts as a signaling protein. SCF stimulates the production and homeostasis of cells within the bone marrow such as blood cells and mast cells. There have been a few cases in which the mutation was passed down through families. However, most cases do not appear hereditary.

Symptoms of mastocytosis are frequently triggered by physical or psychological stress, as well as extreme heat or cold. Certain medications, insect bites, stings, perfumes or odors can also induce or exaggerate symptoms. 

Diagnosis & Tests

A doctor will begin with a physical examination and speak with the patient about symptoms they are experiencing. The presence of fixed, brown, itchy patches on the skin can indicate to the physician that cutaneous mastocytosis may be present.

If mastocytosis is suspected, a skin biopsy is taken, and an elevated concentration of mast cells will confirm the diagnosis. In addition to mast cells being present in the biopsy, substances released by mast cells may also be present such as histamine products, tryptase, prostaglandins, and leukotrienes. Abnormal levels of any of these will aid the physician in their diagnosis.

It can be difficult to differentiate between cutaneous and systemic mastocytosis. Some patients may experience both, so it is important for the doctor to test for any other affected tissues.

A bone marrow biopsy is the most common test to check for systemic mastocytosis. A small amount of bone marrow tissue is extracted and analyzed to check for an increased concentration of mast cells and any genetic mutations that may be present.

Routine blood tests such as a serum test will be performed to check for the mast cell enzyme tryptase. A high amount of tryptase indicates a high concentration of mast cells. If the patient is found to be anemic or has a high level of white blood cells, these are also signs of mastocytosis.

Clinical urine tests are performed to test for elevated levels of histamine products, leukotrienes or prostaglandins. Significant amounts of these substances in the urine can indicate mastocytosis. 

Once diagnosed with mastocytosis, imaging tests such as ultrasounds, computed tomography (CT) scans, and X-rays are used to determine which organs are involved. These images will give physicians a clear idea of what stage the condition is in and what treatment options are necessary. 

Treatment & Therapy

Currently there is no cure for mastocytosis. The majority of treatment options are focused on avoiding triggers which precipitate attacks and exacerbate symptoms. A physician will work with the patient to determine what foods, substances, internal factors and external factors seem to trigger their symptoms and develop a plan to avoid them.

Oral antihistamines and topical corticosteroids are used to relieve most symptoms. Certain medications are also available that counteract the substances released by mast cells. 

The most important aspect of treating mastocytosis is to continually monitor the condition. Patients should stay on schedule with routine labs to monitor the progression of their disease. This helps to know what therapies are working and what may need to be adjusted.

In advanced cases, chemotherapy drugs are used to reduce the number of mast cells. Bone density tests should be performed every two years, as patients with bones affected by mastocytosis often experience osteoporosis and should take supplements to support bone health.

Prevention & Prophylaxis

Due to the nature of mastocytosis, there is no clear way of preventing it. Patients with known allergies should avoid exposure to known allergens to reduce the occurrence of allergic reactions that may trigger a mastocytosis attack.

Patients with ongoing skin lesions and the symptoms listed above should seek treatment from a qualified physician. By identifying mastocytosis as early as possible, it becomes easier to manage the symptoms and avoid triggers. By properly managing the condition, the chances of avoiding bone and organ damage are greatly reduced, providing the best outcome for the patient.