What is Mastocytosis?
Mastocytosis is a rare health condition where there is an excess number of mast cells in various parts of the body. Mast cells are immune cells that protect the body from foreign and harmful agents by releasing chemicals to destroy the invaders.
The increase in mast cells may be observed in different regions of the body, such as bone marrow, skin, liver, small intestine, and the spleen.
The two forms of mastocytosis are cutaneous mastocytosis, mainly affecting the skin and systemic mastocytosis that can involve skin and several organs in the body
Children are usually affected by mastocytosis of the skin (cutaneous) within the initial 2 years, while in adults, mastocytosis affects the bone marrow, skin, and other regions of the body (systemic).
Cutaneous mastocytosis in children tends to improve or completely resolve by adolescence. In contrast, adults with systemic mastocytosis are affected chronically with the condition and may become more serious in a few cases.
Mastocytosis is a result of a mutation in the KIT gene. The protein that is produced from this gene controls the development of mast cells. An error in KIT alters the protein’s function and affects the production of mast cells. This defective protein gets activated due to numerous triggers of mastocytosis, such as:
- Stress due to psychological or emotional situations
- Weather changes, such as drop or rise in temperature
- Sleep issues
- Spicy food
- Specific medicines (eg. cough medicine, morphine, and non-steroidal anti-inflammatory drugs)
- Insect bites
- Vaccinations (in children)
- Bacterial and viral infections
- Trauma to the scalp
Any one of the above triggers can activate the excess production of mast cells, but it is sometimes not clear when exactly the condition gets triggered. Not everyone is affected in the same way by the same triggers.
Mastocytosis presents with varied symptoms depending on the location where the excess mast cells are produced.
In children with cutaneous mastocytosis, the most common symptom include
- Yellow, red, or brown skin lesions in nearly 70-90 percent cases over limbs, chest and abdominal areas
- Skin blisters and swelling.
- In the rare form of diffuse cutaneous mastocytosis (DCM), the scalp and the central area of the skin is affected.
- New lesions develop at sites of scratching (Darier’s sign)
Adults are affected by the following symptoms depending on the site involved
- Freckle-like rash
- Itchy skin rash
- Hives – reddish bumps on the skin appearing suddenly
- Breathing difficulty
- Significant lumps on the skin
- Chronic abdominal pain
- Hepatosplenomegaly (enlarged liver and spleen)
- Increased risk of allergic reactions due to release of large amounts of a chemical called histamine by the mast cells
The three subtypes of systemic mastocytosis include
- Indolent mastocytosis (> 90% cases) – mild to moderate symptoms
- Aggressive mastocytosis – Skin lesions less common but mast cells multiply in various organs. Symptoms are more severe and widespread
- Systemic mastocytosis associated with cancer – Rare cases, where blood cells are affected leading to chronic leukemia
You should consult your family physician when you begin to notice symptoms of rash, breathlessness or diarrhea brought on suddenly by specific triggers.
Childhood mastocytosis is diagnosed based on the following criteria:
- Skin biopsy to detect increase in mast cells (>20)
- Detecting mutations in the KIT gene through genetic or structural tests
- For DSM, diagnostic tests include an abdominal ultrasound (to detect abnormalities in other organs); bone marrow biopsy; and blood or urine tests.
Tests usually done in adults to confirm a diagnosis of systemic mastocytosis include the following
- Skin biopsy to demonstrate mast cell collections
- Blood test to measure serum tryptase levels
- Bone marrow biopsy to look for characteristic findings
- Abdominal ultrasound to look for liver and spleen enlargement
- Bone DEXA scan to assess bone density
According to the World Health Organization (WHO), the criteria to diagnose mastocytosis in adults consists of either one major and one minor feature OR a minimum of three minor criteria.
- Major criterion: Presence of >15 mast cells at the site of inflammation.
- Minor criteria: Expression of mast cell-associated protein receptors; >25% of abnormal mast cells; mutation in the KIT gene.
- Bone marrow biopsy: This is standard procedure to diagnose adults with mastocytosis. It is also useful to distinguish between cutaneous mastocytosis or systemic mastocytosis.
- Skin biopsy: This procedure is performed to detect elevated mast cells in skin in the presence of a rash or hives.
- Measurement of serum tryptase levels: A key diagnostic indicator of mastocytosis is increased production of the serum tryptase enzyme by mast cells.
Mastocytosis treatment is individualized and is influenced by diagnostic outcomes. In general, treatment aims to reduce the symptoms or outcome (excessive itching, diarrhea, stomach pain) of excess mast cells.
Treatment in children involves:
- Avoiding triggers of mast cell production (eg. taking care not to rub inflamed skin, use of moisturizers, avoiding extreme cold or hot temperatures, avoiding stress)
Corticosteroid cream or water-soluble sodium cromolyn cream are applied on inflamed itchy skin with rash.
- Antihistamines (H1 and H2) are prescribed to relieve allergic symptoms.
In DSM, zinc sulphate or topical creams (corticosteroid, sodium cromolyn) are used for skin lesions. In the case of systemic treatment, H1 and H2 antihistamines, oral disodium cromolyn, epinephrine, anti leukotrienes (if other treatments don’t work), and corticosteroids (in cases unresponsive to disodium cromolyn) are prescribed.
Treatment in adults involves:
- Indolent SM -
Avoid triggers; treat symptoms either with self-injectable epinephrine, antihistamines, cromolyn sodium, or rarely with mast cell cytoreductive agents.
- Aggressive SM - Mast cell cytoreductive therapy is used for treatment – for example, 2-chlorodeoxyadenosine; interferon-a with or without prednisone. If these agents have no effect, then other investigative drugs (eg. midostaurin, dasatinib) are considered.
- Systematic mastocytosis associated with cancer: Cancer-related treatment
- Psolaren plus ultraviolet A (PUVA) photochemotherapy is used to treat symptoms in rare cases.
- Imatinib is an FDA-approved drug used to treat rare KIT gene mutations in systemic mastocytosis.
Mastocytosis in children resolves itself before adolescence. However, mastocytosis in adults affects many organs and without prompt treatment, can turn fatal within 3 to 5 years.
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