First, with regard to severe courses of acute Covid-19 illness, it is possible that the patient’s dysfunctional mast cells might be reacting wildly inappropriately excessively to the virus during the actual infection, i.e., while the virus is actually present in the patient’s body, sparking an abnormal “hyperinflammatory” response causing a wide range of inflammation-based problems in one or more of the patient’s vital organs/systems.

It is possible that those dysfunctional mast cells may exhibit either or both of a couple patterns of misbehavior which are important vis-a-vis Covid-19 infection.

Rather, the problem is with the dysfunctional mast cells an MCAS patient has. Normal mast cells are reacting and responding normally to the virus, driving a normal (i.e., helpful) inflammatory response.

To be clear, the concern is not with how normal mast cells (in a healthy person, or even the fraction of the mast cells in the overall mast cell population in an MCAS patient which remain normal) are behaving. However, the specific natures of the symptoms and problems being seen in severe acute Covid-19 illness and in long-haul syndrome are “suggestive” that MCAS could be a key factor. To be clear, no research has been done yet to prove (or disprove) that MCAS is a significant factor in severe acute Covid-19 illness or in Covid-19 long-haul syndrome. Similarly, there are increasing suspicions that MCAS (again, whether recognized to be present in the patient or not yet recognized) may be a key factor, perhaps even the root driving factor, underlying most or all of the symptoms comprising the post-Covid inflammatory syndrome (popularly labeled “Covid-19 long-haul syndrome”) which many Covid-19 patients are also coming to suffer, somewhat independently of whether the course of the initial infection was severe or not. Some health care professionals and researchers in the Covid-19 arena are beginning to suspect that abnormal mast cell activation (i.e., a mast cell activation syndrome (MCAS), regardless of whether that diagnosis was already established in the patient prior to Covid-19 infection or not) may be a key factor, perhaps even the root driving factor, underlying a significant fraction of those cases of acute Covid-19 illness which are particularly severe in nature and come to require hospitalization and seem to bear a significantly higher mortality risk (i.e., risk for death) compared to the majority of the Covid-19-infected population.

General thoughts