Some diseases are caused when there is a change in the instructions in a gene. This is called a mutation. Every person has many mutations. Sometimes these changes have no effect or are even slightly helpful. But sometimes they can cause disease.
Most common diseases are caused by a combination of mutations, lifestyle choices, and your environment. Even people with similar genes may or may not get an illness if they make different choices or live in a different environment.
Thousands of diseases are caused by a specific change in the DNA of a single gene. Many of these diseases are rare. These conditions usually develop when an individual is born with a mutated gene.
If a rare disease runs in your family, be sure to write it down. Do not forget to learn about common conditions that affect your family’s health.