The neuropsychiatric symptoms associated with MCAS are numerous and are results of the chemicals released by mast cells.
Headaches are a very common complaint. They can sometimes be managed with typical remedies (Excedrin, Tylenol) and antihistamine treatment often helps with this symptom quickly. However, in some patients, headaches can be disabling. Diagnosis of migraine is not unusual, with mast cell degranulation having been tied previously to migraines.
Dizziness, lightheadedness, weakness, vertigo, and the feeling of being about to faint are all typical in MCAS, though true fainting spells are less common than in mastocytosis. These symptoms often cause many MCAS patients to be diagnosed with dysautonomia or POTS.
MCAS patients often experience increased activation of sensory and motor nerves. This manifests as generic neurologic symptoms, sometimes several at once, like tingling, numbness, paresthesia and tics. Tics generally do not spread from the place they initially present. Paresthesias seem to progress for a period of time, then wane and disappear. Extremities are most commonly affected.
EMG and nerve conduction studies are typically normal or abnormal in a way that is not diagnostic. These tests sometimes reflect a possibility of chronic inflammatory demyelinating polyneuropathy (CIDP.) These patients also sometimes are positive for monoclonal gammopathy of unknown significance (MGUS), a blood marker that has been tied to multiple myeloma. However, in these patients, the MGUS is believed to be an effect of the MCAS.
Another subset of patients are diagnosed with subacute combined degeneration (SCD), a deterioration of the spinal cord associated with B12 deficiency. They are sometimes treated for pernicious anemia despite lack of hematologic support for this diagnosis.
Prostaglandin D2 is a known effector of nerve damage and has been blamed for many of the neurologic symptoms seen in MCAS. Astrogliosis, abnormal proliferation of astrocytes (nerve cells in the brain), and demyelination (loss of the insulating cover for nerves that allows the body to send signals) are markers of neurodegeneration. These factors cause scarring and inhibit nerve repair mechanisms. PGD2 is made by an enzyme called hematopoietic PGD synthase. In mice that don’t make this enzyme, these kinds of neuroinflammation are suppressed. Treatment of normal mice with an inhibitor of this enzyme (HQL-72) also decreases these actions. This indicates that PGD2 is critical in causing neuroinflammation including demyelination. PGD2 also activates pain receptors strongly, causing sometimes profound neurologic pain.
PGD2 is also the most potent somnagen known, meaning that it induces sleep more strongly than any other molecule. MCAS patients report inordinately deep sleep, “mast cell coma.” This is likely due to excessive PGD2. Conversely, some MCAS patients also have insomnia, from excessive histamine.
I have written at length before about cognitive and psychiatric manifestations of mastocytosis, which are the same as in MCAS. Cognitive and mood disturbances are all kinds are reported. Brain fog, including short term memory troubles and word finding problems, is the most common symptom. Irritability, anger, depression, bipolar affective disorder, ADD, anxiety, panic disorders and even sometimes frank psychosis can present. Such symptoms in mastocytosis patients were referred to as mixed organic brain syndrome, a term coined in 1986. The important aspect of these symptoms in MCAS is that they are caused by mast cell activation. As such, they are most effectively treated by managing mast cell release symptoms. Some patients do find relief in some psychiatric medications, but the psychiatrist should be aware that these symptoms are part of mast cell pathology.
Additionally, PTSD is not rare in MCAS patients. This is most often due to the trauma from negative interactions with the medical industry.
Autism is significantly increased in patients with mastocytosis. Similar findings are beginning to surface with MCAS patients. Interesting, most autism spectrum disorder patients have food intolerance and general allergic symptoms. A future post will discuss this in more detail.
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Rogers MP, et al. Mixed organic brain syndrome as a manifestation of systemic mastocytosis. Psychosom Med. 1986 Jul-Aug;48(6):437-47.