Definition of «to underlie the illnesses»

The phrase "to underlie the illnesses" means that something is the main cause or foundation of the sicknesses or diseases.

They are the symptoms of underlying illness in the marriage. (theresolutioncenterindy.com)
It is often caused by underlying illness and congenital and hereditary conditions. (pets.webmd.com)
Always make sure that you have no serious underlying illness or disease that could be compromising your health. (bewell.com)
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