MCAS patients often have a whole host of metabolic irregularities. Abnormal levels of electrolytes are very common, as are mild increases in liver function tests, including aspartate transaminase, alanine transaminase and alkaline phosphatase. Magnesium levels low enough to cause symptoms is not common, although the reason for this is not known.
Vitamin D deficiency is often present in MCAS. In one study looking at children with asthma, low vitamin D was correlated with decreased lung function and exercise sensitivity. In MCAS patients, there is no obvious relation to osteoporosis. Many people receive vitamin D supplements to correct low levels, but it is not clear if there is any benefit to this.
Hypothyroidism (including Hashimoto’s thyroiditis) and elevated levels of TSH are often seen in MCAS patients. Previous studies have linked hypothyroidism to increased mast cells in bone marrow. In mice, TSH has shown to increase both the mast cell population in the thyroid and to trigger degranulation. Hyperthyroidism is sometimes seen in MCAS patients, but much less frequently. Antithyroid antibodies (TPO) are often high, sometimes extremely high, and sometimes without obvious clinical thyroid disease.
Hyperferritinemia is not unusual in mast cell disease, including MCAS. 18% of ISM patients have high serum levels of ferritin. It is often misinterpreted as hemochromatosis, even in the absence of the HFE mutation. MCAS patients with a history of red cell transfusion are often told they have hemosiderosis, even when serum ferritin is much higher than to be expected from hemosiderosis. High ferritin in MCAS patients is probably secondary to systemic inflammation. The widely variable nature of the ferritin levels is indicative of inflammation.
MCAS is also associated with obesity and diabetes mellitus (types I and II), all of which are systemic inflammatory conditions. MCAS patients often have lipid abnormalities. Hypertriglyceridemia is the most common presentation, but there are many variations. Lipid issues that have been resistant to treatment with statins are often reversed quickly when MCAS patients are effectively managing their mast cell issues.
MCAS is also heavily associated with metabolic syndrome. (There will be a full post on this tomorrow.)
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