A new case report published in Annals of Allergy, Asthma Immunology describes how an extensive diagnostic evaluation helped physicians distinguish exercise-induced anaphylaxisAnaphylaxis A severe allergic reaction that can turn fatal without treatment. Patients with SM are at a higher risk of developing anaphylaxis. from mast cellMast cell A type of white blood cell produced in the bone marrow. They help defend against infections and play a key role in allergic reactions. In SM, mast cells become overactive and build up throughout the body. disorders like systemic mastocytosis (SM) and mast cell activationMast cell activation Describes when mast cells release histamine and other mediators into the blood stream in response to an allergen or other trigger. This leads to symptoms like fatigue, rash and, in severe cases, anaphylaxis. syndrome (MCAS) in a military pilot. Researchers say the findings underscore the importance of identifying the correct diagnosis when symptoms overlap.
The report centers on a 54-year-old military pilot who experienced recurrent hives, flushing, lightheadedness and episodes of near-fainting after strenuous exercise. Unlike food-dependent exercise-induced anaphylaxis, his reactions occurred independently of eating or medication use.
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Initial cardiac testing found no evidence of heart disease, but an exercise stress test triggered severe low blood pressure and fainting shortly after exercise. This prompted further investigation into a possible mast cell disorder.
Physicians evaluated several possible causes, including SM, hereditary alpha-tryptasemia, MCAS and exercise-induced anaphylaxis. Blood tests, KIT D816V mutation testing and a bone marrow biopsyBone marrow biopsy A procedure to collect a sample of bone marrow using a needle. Often used to examine the characteristics of mast cells and diagnose SM. ruled out systemic mastocytosisMastocytosis Rare disease caused by the buildup of mast cells. Cutaneous mastocytosis primarily affects the skin and is more common in children, while systemic mastocytosis affects internal organs and is more common in adults., while genetic testing excluded hereditary alpha-tryptasemia.
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To reach a definitive diagnosis, doctors had the man undergo a supervised exercise challenge while receiving continuous cardiovascular monitoring during cardiac catheterization.
Exercise consistently reproduced his symptoms, including flushing, hives, fainting and a blood pressure drop to 67/46 mmHg. At the same time, blood tests showed marked increases in tryptaseTryptase A protein enzyme that is primarily produced by mast cells and stored in small pockets within the cells, known as granules. High levels of tryptase are a key indicator of SM., histamineHistamine A chemical released by mast cells when they are activated. Histamine causes many of the allergy-type symptoms in mastocytosis, including flushing, itching and hives. and prostaglandin D2, which are all markers of mast cell activation. Together, these findings confirmed food-independent exercise-induced anaphylaxis rather than MCAS.
Doctors prescribed a second-generation H1 antihistamine to manage chronic hives and an epinephrineEpinephrine Also called adrenaline, this hormone is used in emergency situations to reverse symptoms during a severe allergic reaction (anaphylaxis). autoinjector for exercise-induced anaphylaxis. The man was also advised to gradually increase exercise, stop activity at the first sign of symptoms and avoid exercising alone.
The authors note that distinguishing exercise-induced anaphylaxis from MCAS can be difficult because both conditions involve mast cell activation. They conclude that careful evaluation, including exclusion of clonal mast cell diseaseMast cell disease A group of conditions in which mast cells behave abnormally by building up in excess, releasing chemicals too easily or both. Includes mastocytosis, mast cell activation syndrome and hereditary alpha-tryptasemia. and assessment of symptom triggers, is essential, particularly for people in high-risk occupations where an incorrect diagnosis could have serious consequences.
