What are mast cells?
Mast cells are a type of white blood cell. They are packed with histamine, a chemical released when you get an allergic reaction, and heparin, a chemical which stops the blood from clotting. Mast cells are hard-working cells that have many functions, including helping to fight infection and healing wounds.
However, mast cell disorders can occur in which too many cells are produced or they become overactive.
What are the types of mast cell disorder?
This is the term used when too many mast cells are produced. There are many different types of mastocytosis and it would be confusing to list them all. The types you are most likely to come across are:
- Those involving the skin (cutaneous).
- Those which involve lots of different tissues of the body (systemic).
Much less commonly there is a localised type in which clumps of mast cells gather in one place.
Mast cell activation syndrome
You may also see mast cell activation syndrome (MCAS) called mast cell activation disorder (MCAD). The mast cells are present in normal numbers but they are triggered to release their chemicals more readily than usual. The symptoms are generally the same as mastocytosis.
Localised mast cell disorder
Rarely, clumps of mast cells can develop in one area of the body.
Who gets a mast cell disorder?
These conditions are not very common. It occurs in about 1 in 150,000 people. The most common type - urticaria pigmentosa (see Symptoms, below) - is seen in 1 person in every 1,000 who attends a skin (dermatology) clinic.
What are the symptoms of mast cell disorders?
When larger than normal numbers of mast cells are present in the skin they commonly cause a condition called urticaria pigmentosa. Another less common condition called diffuse cutaneous mastocytosis is also sometimes seen.
By James Heilman, MD (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
- This usually starts in babies a few months old but can go on for years. It causes a rash to appear anywhere on the body made of light brown, itchy raised patches.
- If you rub the patches, they become red and swollen and blisters develop. This is called Darier's sign.
- Rarely, after rubbing or applying heat to the skin, a severe allergic effect (an anaphylactic reaction) can occur .
- Your child may develop dermographism - this is a condition in which you can 'write' on the skin with a blunt object.
- The condition usually gets better as your child gets older and usually disappears by the time they reach their teens. Rarely, an adult form can develop.
Diffuse cutaneous mastocytosis
- This usually occurs in children less than 1 year old.
- They develop a very itchy rash with yellow, thickened skin.
- Large blisters can appear for no reason or after a very light amount of rubbing.
- If large areas of skin are involved, bodily symptoms can develop such as flushing, headache and the sensation of having a 'thumping' heart (palpitations). Tummy pains, diarrhoea and breathlessness can occur., The child can go into shock and become very ill. Some children have died of this condition.
Rarely, clumps of mast cells can form a nodule in the skin, which is usually red, brown or yellow in colour. This is called a mastocytoma. Even more rarely, a cancerous lump called a mast cell sarcoma can develop.
This can cause a whole range of symptoms depending on the parts of the body where large numbers of mast cells are found. For example:
- Skin - flushing of the face, urticaria pigmentosa (see above).
- Digestive system - tummy pains, diarrhoea, pale stools that are difficult to flush, feeling sick (nausea) or being sick (vomiting), acid indigestion, stomach ulcers.
- Swelling of the liver or spleen.
- Circulatory problems - fainting, low blood pressure, anaphylactic shock.
- Anaemia; other problems with the blood or bone marrow.
- Fractures of the bones (because of bone marrow involvement).
- Swollen lymph nodes.
- Breathing difficulties.
- Headaches, pins and needles, numbness.
Did you find this information useful?
- Cardet JC, Akin C, Lee MJ; Mastocytosis: update on pharmacotherapy and future directions. Expert Opin Pharmacother. 2013 Oct 14(15):2033-45. doi: 10.1517/14656566.2013.824424.
- Maculopapular cutaneous mastocytosis; DermNet NZ, 2014
- Pardanani A; Systemic mastocytosis in adults: 2017 update on diagnosis, risk stratification and management. Am J Hematol. 2016 Nov 91(11):1146-1159. doi: 10.1002/ajh.24553.
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