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Characteristics

Mastocytosis is a rare disorder in which certain immune cells, called mast cells, build up in the body. When mast cells detect a germ or virus, they set off an inflammatory (allergic) response by releasing a chemical called histamine. In addition to this, mast cells play a role in wound healing, bone growth and the formation of new blood vessels. In patients with mastocytosis, the growth of mast cells is poorly controlled, in most cases due to an acquired (i.e., not inherited) mutation in the KIT gene.

There are two main types of mastocytosis: cutaneous and systemic. Cutaneous mastocytosis occurs more often in children and is characterized by a build-up of mast cells in the skin leading to red or brown, itchy skin lesions. In contrast, systemic mastocytosis mainly affects adults and affects other parts of the body. In patients with systemic mastocytosis, mast cells accumulate in the bone marrow and different organs, such sch as the intestine, and less commonly the brain, the heart or the lungs. In these organs, the resulting chronic inflammation can cause significant organ damage.

In patients with mastocytosis, specific activities or environmental factors can trigger an attack. This includes rubbing or friction on the skin, physical activity, certain insect bites, the intake of specific food or medication, sudden temperature changes, or emotional stress.

Symptoms

As already indicated, cutaneous mastocytosis is characterized by red or brown itchy skin lesions. These lesions can form all over the body and can sometimes blister.

In patients with systemic mastocytosis, attacks come with a wide range of symptoms. This includes skin reactions (e.g., itching, or flushing), gastro-intestinal symptoms (e.g., nausea, vomiting, abdominal pain, diarrhea) and muscle or joint pain. In addition, patients may also experience other allergy-like symptoms such as shortness of breath, a swelling of the throat and changes in the blood pressure.

Patients with mastocytosis also have an increased risk of developing a severe and life-threatening allergic reaction, known as an anaphylaxis. This severe allergic reaction is caused by a massive release of histamine in the blood and is characterized by a rapid heartbeat, fainting, loss of consciousness and shock. Patients who have a severe allergic reaction, may need an injection of epinephrine.

Other complications of mastocytosis include poor blood clotting, peptic ulcer disease (as a result of chronic stomach irritation), a reduced bone density and organ failure.

Diagnostic tests

The first step in the diagnosis for cutaneous mastocytosis consists of a physical examination of the skin. In this, a physician will rub an affected area of the skin to see if it becomes red, inflamed, and itchy. When this test points towards mastocytosis, a skin biopsy will be taken to check for the presence of mast cells.

The diagnosis for systemic mastocytosis usually starts with a blood test to measure the basal serum total tryptase level. Tryptase is an enzyme that is released by mast cells and its level is therefore increased in patients with systemic mastocytosis. Subsequently, a bone marrow biopsy is usually performed. This test is done because mast cell precursors originate in the bone marrow before migrating to other organs to mature. In patients with mastocytosis, these precursors are more abundant in the bone marrow than in healthy individuals. Further tests may include an ultrasound to evaluate whether the liver or spleen are enlarged and a DEXA scan to measure the bone density. In addition to this, a biopsy can be taken from affected organs to evaluate the presence of mast cells. Finally, genetic testing can be ordered to assess whether a patients harbors a mutation in the KIT gene.

Treatments

The first important part of managing mastocytosis consists of identifying and avoiding factors that may trigger an attack, such as certain food, medications, or insect bites.

To relieve an allergic reaction, antihistamines, leukotriene modifiers, mast cell stabilizers, or corticosteroid creams are generally used. To reduce inflammation, doctors may prescribe oral steroids. Depending on the development of other symptoms, other medication can be used, including drugs to reduce stomach acid or agents that relieve bone pain. For some patients with cutaneous mastocytosis, ultraviolet light therapy can be considered. In addition to this, patients with mastocytosis should make sure to always have an epinephrine pen at hand in case they develop an anaphylactic shock.

For patients with aggressive systemic mastocytosis, chemotherapy with cladribine can be considered. In addition, also targeted therapy with midostaurin, or imatinib are being used to treat patients with systemic mastocytosis.

Relevant patient organisations

Get connected to different patient organisations that connect you to people with the same medical history. Support amongst peers helps the burden and stress of the daily challenges that come with disorders.

Find below some organisations we can recommend.

Be aware that these groups operate mainly in Dutch or French given their local nature, don’t hesitate to contact them nevertheless.

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