Mast Cell Activation Syndrome Quiz

Mast cells are allergy cells that cause allergic symptoms by releasing products called “mediators” stored inside them or made by them. They are triggered to release these products in a process called “activation”. Usually mast cells are activated by known triggers such as allergic antibody, medications or infections. The released mediators go on to produce allergic symptoms such as sneezing, wheezing and itching. In more severe reactions such as anaphylaxis, the symptoms can be hives, swelling, low blood pressure, fainting, difficulty breathing, nausea and vomiting or profuse diarrhea.

Mast Cell Activation Syndrome (MCAS) is a condition in which the patient experiences repeated episodes of these symptoms but the trigger cannot be identified. The exact combination of symptoms and the organ systems affected can vary from patient to patient, but the cases are similar in the mast cell mediators that are released and the treatments that are effective.

Question 1
MCAS is a condition with persistent symptoms of mast cell mediator release present day in and day out.

False. MCAS is a condition with discreet, intermittent episodes of anaphylactic symptoms.

Question 2
The anaphylactic symptoms typical of MCAS are:
A. Hives and nausea/vomiting
B. Rapid heartbeat and hoarse voice (stridor)
C. Passing out and wheezing
D. Swollen face and stomach cramping
E. All of the above

E. Anaphylaxis typically involves more than one symptom in more than one part of the body at the same time. In MCAS symptoms are seen in two or more of the four main organ systems: heart, lung, skin and gastrointestinal tract. Symptoms of anaphylaxis seen in MCAS include:

  • Swollen throat or swollen areas of the body
  • Wheezing
  • Passing out
  • Rapid heart beat
  • Trouble breathing
  • Hoarse voice
  • Trouble swallowing
  • Stomach cramping
  • Hives and itching
  • Nausea and vomiting
  • Flushing

The most dangerous symptoms are low blood pressure, breathing difficulty and loss of consciousness, all of which can be life-threatening.

Question 3
Mast cells can be stimulated to release mediators by outside stimuli such as allergens (secondary activation) or by internal stimuli (primary activation). Primary activation is usually seen in clonal mast cell disorders.

True. The primary activation disorders are clonal mast cell disorders in which activation is caused by mutations that allow uncontrolled growth and overproduction of mediators.

Question 4
Idiopathic MCAS is due to:
A. Secondary mast cell activation
B. Primary mast cell activation
C. Neither

C. The triggers for activation in idiopathic MCAS are unknown – hence the term “idiopathic”. Secondary mast cell activation means the triggers for activation are recognized external triggers, such as allergic antibody or an infectious process. Primary mast cell activation means activation produced by mutations within the mast cells, which may lead to overproduction of identical cells (clones).

Question 5
The first line of treatment for life-threatening anaphylaxis in both primary and secondary mast cell activation is:
A. Diphenhydramine (Benadryl)
B. Prednisone
C. Aspirin
D. Epinephrine

D. Autoinjectable epinephrine should be given early to help stop or slow down the reaction from getting worse. People with a history of anaphylaxis or MCAS should carry epinephrine with them at all times.

Question 6
In addition to epinephrine, specific treatment for episodes of MCAS includes:
A. Aspirin
B. Leukotriene receptor antagonists
C. Corticosteroids
D. Antihistamines
E. All of the above

E. Agents that block the effects of mast cell mediators are effective in reducing the symptoms during episodes.

Question 7
In MCAS the cause of activation is idiopathic i.e. unknown. Normal activation of mast cells is usually “secondary to” known triggers. All of the following are common secondary causes except:
A. Allergens
B. Non-ionic low-osmolal x-ray dyes
C. Autoimmune conditions
D. Medications
E. Infectious diseases

B. Also known as non-ionic low-osmolal contrast media (LOCM), the newer radiocontrast dyes have a low incidence of reactions due to triggering of mast cells as compared to the older hyperosmolal contrast dyes (HOCM). Most centers now use the non-ionic LOCM since they are safer and evaluating, observing and treating reactions adds time and cost to procedures.

Question 8
Collection of blood and urine samples to measure mediators to document MCAS should start?
A. 12 to 24 hours after start of the episode
B. 30 minutes to two hours after start of the episode
C. Six to 12 hours after start of the episode
D. 24 to 48 hours after start of the episode

B. Documenting the mast cell activation in MCAS requires starting to measure mast cell mediators immediately. Since these are not standard laboratory tests, patients should work with their local allergist who can communicate with emergency department and lab personnel to assure the tests are ordered and completed in a timely fashion.

You answered   questions correctly.


Learn more about Mast Cell Activation Syndrome symptoms, diagnosis, treatment and management.
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