A booster dose of Moderna’s COVID-19 vaccine (mRNA-1273) likely triggered a dangerous immune response in a patient with systemic mastocytosis (SM), leading to severe 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., high fevers, rash, vomiting and systemic inflammation, according to a case report published recently in Inflammation Research.
This case study highlights how certain vaccines can, in rare cases, cause major metabolic, lipid and cytokine disturbances in people with 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 — and how quick intervention may be life-saving when this occurs.
Though “the European and American 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. societies recommended mRNA-based SARS-CoV-2 vaccinations for all mastocytosis patients over 16 years of age,” they have done so “with certain precautions such as prolonged supervision after vaccination and pre-medication with 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. 1 and 2 receptor antagonists,” noted the case study’s authors.
The case describes a 43-year-old man with indolent SMIndolent SM A subtype of nonadvanced SM caused by the abnormal accumulation of mast cells in the bone marrow and other organs. Indolent SM accounts for around 90% of SM cases.. Within 24 hours of vaccination, the patient experienced escalating symptoms that met criteria for systemic inflammatory response syndrome, including a fever and a rapid heart rate of 133 beats per minute. Blood tests revealed a 26% drop in platelet count, severe elevation 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. (a mast cell marker) and a peak histamine level of 18 ng/ml, which is considered life-threatening.
The patient was treated with antihistaminesAntihistamines Medications that block the effects of histamine, the chemical found in mast cells that is responsible for many of the symptoms of SM, as well as many allergic reactions. and tocilizumab, a drug that blocks interleukin-6 (IL-6), a key inflammatory molecule. Clinical symptoms began to improve within 12 hours of treatment.
Read more about SM causes and risk factors
Over a year later, the same patient had another mast cell activation event following a confirmed COVID-19 infection. Although symptoms were less severe, IL-6 was again elevated and tocilizumab was used with good effect.
“Since IL-6 is consistently highly elevated during MCA [mast cell activation] events in this patient, the anti-IL-6 receptor antibody tocilizumab was administered in both events,” explained the authors of this report. “Considering the pro-inflammatory role of IL-6, the strong positive correlation between IL-6 concentrations and mortality, and the adverse event profile of tocilizumab in thousands of rheumatoid arthritis patients likely treated multiple times, single administration of tocilizumab during severe MCA events is justified.”
This repeat episode strengthens the link between virus exposure and mast cell activation in patients with SM. The authors noted that lab experiments on mast cell lines exposed to both Moderna and Pfizer mRNA vaccines showed variable and inconclusive effects, but that cell damage was consistently observed.
While the benefits of COVID-19 vaccination still outweigh the risks for most, this case underlines the importance of tailored care for individuals with mast cell diseases. For patients with SM, clinicians may consider preemptive strategies or emergency planning around vaccination to reduce potential harm.
Sign up here to get the latest news, perspectives, and information about SM sent directly to your inbox. Registration is free and only takes a minute.
