Symptoms and Triggers of Indolent Systemic Mastocytosis

Indolent systemic mastocytosis (ISM) symptoms can be hard to pin down. They show up in different parts of the body, they can flare without warning, and they can look and feel a lot like other conditions. Knowing what to watch for makes them easier to describe to your doctor, whether you are newly diagnosed with ISM or have lived with it for years.^1-3

Why ISM symptoms happen

Mast cells release chemicals called mediators when they are activated. Mediators are the chemicals – such as histamine – responsible for the swelling, itching, and flushing you experience during an allergic reaction. In ISM, you have too many mast cells releasing too many of these chemicals, and that is where most symptoms come from.¹
Other symptoms can come from the mast cells themselves building up in tissue and organs, rather than from the chemicals they release. A buildup of mast cells in the skin, for example, can cause raised patches of brownish skin that sting or itch.^1,2

Symptoms you may notice

Systemic mastocytosis is rare, affecting an estimated 1 in 10,000 to 20,000 people worldwide.²

ISM affects people differently. You may have only a few symptoms, and they may change over time. They also might come and go in “episodes” or “flares” of greater intensity at unexpected times.^1-3

Common ISM symptoms include:^1,2,4

• Skin – Flushing of the face, neck, and chest. Itching, hives, and swelling. Some people have brownish patches called urticaria pigmentosa.
• Digestive – Belly pain, bloating, reflux, diarrhea, nausea, and vomiting.
• Heart and blood pressure – A fast or irregular heartbeat, low blood pressure, lightheadedness, and fainting.
• Brain and mood – Brain fog, trouble concentrating, headache, anxiety, and low mood.
• Breathing – A stuffy nose, shortness of breath, wheezing, and cough.
• Bones and muscles – Bone pain, muscle pain, and bone thinning.
• Whole body – Severe tiredness.

Some of these might normally be explained away. Brain fog, for example, can be the result of a busy week. Tiredness can be from not getting good quality sleep. Belly trouble can be from something you ate. In ISM, though, these symptoms can all be part of the same larger picture.

Anaphylaxis: A symptom to take seriously

Anaphylaxis is a severe allergic reaction that comes on fast. Nearly half of all people with systemic mastocytosis will experience a severe allergic reaction.²

Warning signs include trouble breathing, swelling in the throat, a sudden drop in blood pressure, a weak pulse, and fainting. It can happen after things like an insect sting or bite, or can be a reaction to a medication.¹

All people with mast cell diseases like systemic mastocytosis should carry 1-2 doses of epinephrine with them at all times. If you have signs of anaphylaxis, use your epinephrine right away. Then call 911, even if the symptoms start to ease. The effects of epinephrine can wear off after a few minutes, and a second dose may be needed if the first does not work well enough or symptoms come back before help arrives.^3,4-6

Doctors also may recommend that mast cell disease patients wear a medical bracelet or carry their medical information with them in case of an emergency. This allows others to be alerted to your needs and get medical attention for you if you are unable to get it for yourself.⁶

What can trigger ISM symptoms?

A trigger is anything that activates your mast cells. Common ones fall into a few groups:^3,4

• Temperature – Heat, cold, and sudden changes between the two
• Physical – Exercise, friction or pressure on the skin, vibration, and sunlight
• Stress and fatigue – Emotional stress, physical stress, and pain
• Food and drink – Alcohol and spicy foods are common triggers
• Drugs – NSAIDs, opioids, muscle relaxers, some antibiotics, local anesthetics, and contrast dye used for imaging
• Stings and bites – Bees, wasps, fire ants, and other biting insects
• Strong smells – Perfumes, cleaning products, and chemical odors
• Infections – Viral, bacterial, and fungal

Finding your own triggers

Triggers are not the same for everyone. Two people with ISM can react to completely different things, so part of managing ISM is working out which ones are yours. Avoiding them is the foundation of day-to-day symptom control.^1,5

Writing things down helps. After a flare, note what you ate, where you were, the temperature, your stress level, and any new prescription or over-the-counter medications or supplements you took. Patterns may show up over the course of several weeks that are difficult to spot in the moment.

How ISM symptoms are managed

Avoiding your triggers comes first. Beyond that, most treatment works by blocking or calming the chemicals your mast cells release, using drugs such as antihistamines. Your doctor may add others depending on which symptoms affect you most.^4,5

Talk to your doctor

Symptoms that seem unrelated to each other could be related to ISM. Bring the whole list to your appointment, even the parts that feel too small to mention.

If a symptom is new, getting worse, or frightening you, do not wait for your next scheduled visit. Call your doctor right away and seek medical attention immediately if you experience a sudden onset of severe symptoms.