What is an underlying disease? For example, cerebrovascular diseases include cerebral infarction and cerebral hemorrhage, and cerebral infarction is a major disease, which corresponds to underlying diseases such as hypertension, diabetes, hyperlipidemia, hyperhomocysteinemia, heart disease, and other chronic inflammatory diseases. diseases. For coronary heart disease is now the main disease, it is also the underlying diseases such as hypertension, hyperlipidemia, diabetes mellitus, etc. These are called underlying diseases.