Mastocytosis is a rare condition caused by excessive amounts of mast cells gathering in body tissues. These cells release large amounts of histamine and other chemicals into the blood, causing symptoms such as a skin rash, itchy skin and hot flushes.
Mast cells play an important role in the immune system and are found in certain parts of the body, such as the skin and the lining of the lungs and stomach.
Types of mastocytosis
There are two main types of mastocytosis:
In cutaneous mastocytosis, mast cells gather in the skin. It usually only affects children – three-quarters of cases develop in children aged one to four. It is also known as paediatric mastocytosis.
The most common symptom of cutaneous mastocytosis is abnormal growths (lesions) on the skin, such as blisters and spots which can form a rash on the body.
In systemic mastocytosis, mast cells gather in body tissues, such as the skin, organs and bones and can affect any part of the body. The condition mainly affects adults.
People with the condition experience attacks, lasting 15-30 minutes, when their symptoms are severe. During an attack they may have:
- allergic reactions, such as itching and flushing
- gut symptoms, such as vomiting and diarrhoea
- pain in muscles and joints
- changes in mood, headaches and episodes of severe fatigue (tiredness)
These attacks are often triggered by:
Systemic mastocytosis is also known as mast cell disease.
Read more about the symptoms of mastocytosis.
There are three subtypes of systemic mastocytosis, described below.
- indolent mastocytosis (accounting for 90% of cases) – symptoms are usually mild to moderate and vary from person to person
- aggressive mastocytosis – mast cells invade organs such as the spleen, liver and digestive system, so symptoms are more wide ranging and severe (but skin lesions are less common)
- systematic mastocytosis with associated haematological (blood) disease – the person also develops a condition affecting blood cells, such as chronic leukaemia
The cause of both types of mastocytosis is not fully known although there is thought to be an association with a genetic mutation known as the c-KIT mutation. A genetic mutation happens when normal instructions carried in certain genes become ‘scrambled’. This means some of the body’s processes will not work in the normal way.
Severe allergic reaction
Because of the excessive amounts of mast cells and their potential to release large amounts of histamine into the blood, people with mastocytosis have an increased risk of experiencing a severe and life-threatening allergic reaction known as anaphylaxis.
If you or your child are diagnosed with mastocytosis, you may need to carry an adrenaline injection kit, which can be used to prevent the symptoms of anaphylaxis from getting worse.
Symptoms of cutaneous mastocytosis usually improve over time. In most cases the disease goes away on its own by the time a child has reached puberty.
The outlook for systemic mastocytosis can vary depending on the type you have. Indolent systemic mastocytosis should not affect life expectancy, but other types can. Some people develop a serious haematological condition, such as chronic leukaemia.
There is no cure for mastocytosis. Treatment is based on trying to relieve symptoms with medication.
Read more information about how mastocytosis is treated.
How common is mastocytosis?
Cutaneous mastocytosis is the most common form of the condition, but is still rare in general terms. It is estimated only one in every 1,000 visits to a dermatologist (specialist in treating skin conditions) is due to cutaneous mastocytosis.
Systemic mastocytosis is thought to be much rarer, although exactly how rare is uncertain. One estimate is that one in 150,000 people in England have systemic mastocytosis.