Long COVID, which is also called long-term COVID or post-COVID syndrome, may be linked to 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), according to findings from an article published in the Evening Standard—a regional newspaper from London, England.
The presence of systemic mastocytosis (SM) increases an individual’s risk for the future development of MCAS. The American Academy of Allergy, Asthma, and Immunology notes that the most accurate technique for the diagnosis of MCAS is with the use of 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. and aspirate. This method is utilized for diagnosing SM as well.
Such rare immunologic disorders as MCAS are thought to be secondary conditions that are triggered by having experienced a COVID-19 infection.
The National Institute for Health and Care Excellence defines long COVID as “symptoms that arise during or after an infection and last longer than 12 weeks, which cannot be attributed to another illness.” Long COVID is a chronic condition in which a wide range of symptoms are reported. These symptoms may be ongoing, improve, or worsen over time
Read more about SM testing and diagnosis
In patients who experience recurrent, sudden-onset episodes of severe systemic symptoms associated with MCAS, 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. is one of the 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. mediators being released. Mast cells are known to release chemical mediators incorrectly and abundantly among individuals with MCAS.
Patients with MCAS can experience an array of symptoms. Primary symptoms of MCAS involve dermatologic, gastrointestinal, cardiovascular, neurologic, and pulmonary problems.
Episodes of MCAS are deemed idiopathic, because the mechanisms that cause these episodes remain to be elucidated. This means that such episodes are not linked to an allergic reaction or to the result of a recognized condition that can trigger normal mast cells.
The most serious symptoms, in which high quantities of mast cell mediators are released, include the following indicators of anaphylaxisAnaphylaxis A severe allergic reaction that can turn fatal without treatment. Patients with SM are at a higher risk of developing anaphylaxis.:
- Allergic skin reactions, such as hives and itching
- Swelling of the throat, tongue, and lips
- Difficulty breathing
- Low blood pressure
- Severe diarrhea
Along with bone marrow biopsy and aspirate, additional laboratory tests utilized for diagnosing clonal MCAS comprise flow cytometry analysis and evidence of mast cell mediators, such as histamine and some cytokines. Treatment with mast cell mediator blockers and inhibitors can help as well.
“[T]he variability of symptoms and ‘lack of flagrant acute presentation’ make MCAS challenging to diagnose,” the author concluded.
