Case history
Case history #1
A 57-year-old man is brought to the emergency department by ambulance for treatment of anaphylaxis triggered by a wasp sting. Initially, he had felt dizzy and was flushed and itchy but within a few minutes he had lost consciousness. On arrival at the scene, the paramedics administered epinephrine (adrenaline). In the emergency department, he has difficulty maintaining his blood pressure (which drops to 65 mmHg systolic) and he is given a further dose of intramuscular epinephrine together with intravenous fluids. His systolic blood pressure rises to 95 mmHg and he is observed for 12 hours before discharge. His acute tryptase level is 45 ng/ml during the anaphylactic episode. The patient is referred to an allergist. He has specific IgE antibodies for wasp venom (0.83 kU/l (reference <0.10 kU/l), and a diagnosis of venom allergy is confirmed. On further questioning about his medical history, he mentions a previous reaction to a wasp sting 8 years earlier. On that occasion, he had had cutaneous symptoms (generalized urticaria, flushing) and gastrointestinal symptoms (abdominal discomfort and diarrhea) but did not seek emergency care. A baseline tryptase test finds a level of 16 ng/ml and a provisional diagnosis of secondary MCAS is made. There are no typical skin lesions suggestive of mastocytosis but a KIT D816V mutation is detected in the peripheral blood. A bone marrow investigation is performed and he receives the diagnosis of indolent systemic mastocytosis concomitant with his secondary MCAS (i.e., mixed MCAS). Shortly after diagnosis, venom-specific immunotherapy is started.
Case history #2
A 33-year-old woman is referred to an allergy/immunology clinic due to unexplained recurrent anaphylaxis that started when she was 8 years old. Her history includes 10 episodes of anaphylaxis that manifested as a combination of cardiovascular, cutaneous, and gastrointestinal symptoms. In addition, she had experienced around 90 episodes of less severe symptoms related to mast cell mediators, with pruritus and/or gastrointestinal symptoms (abdominal cramps and diarrhea). The patient has no history of allergies or asthma and her allergy workup, including skin prick test (inhalation and food panel) and specific IgE tests, is unremarkable. She has a total IgE level of 30 kU/L. Her baseline tryptase levels are between 2.5 ng/ml and 3.5 ng/ml. A bone-marrow biopsy shows no signs of clonality. During 10 years of follow-up under the specialist clinic, the patient experiences 7 further episodes of anaphylaxis. From the total of 17 anaphylaxis episodes, 15 involve a presentation with syncope. An acute tryptase is measured during two such episodes and found to be 11 ng/ml and 12 ng/ml. After starting high-dose maintenance desloratadine, she experiences no anaphylaxis episodes in the following 4 years. A diagnosis of idiopathic MCAS is confirmed.
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