Diseases are classified as rare if fewer than 200,000 people are diagnosed with the condition. The National Institutes of Health lists 7000 rare diseases, affecting an estimated 25 to 30 million people. People inherit most rare diseases, but there are those that randomly appear due to odd gene mutations. Historically, pharmaceutical companies have chosen not to develop treatments for these diseases. As a result, medical professionals refer to these rare genetic disorders as orphan diseases. Some are fatal, but others have no severe complications and ultimately do not affect the individual's quality of life.
When a protein called prion causes normal brain proteins to fold abnormally, affected individuals may develop a prion disease such as fatal familial insomnia, which involves the PRNP gene. FFI is the result of changes in the thalamus, the part of the brain that regulates sleep and consciousness, motor control, and many many other bodily functions. The disease causes insomnia, weight loss, increased or decreased body temperature, and rapid dementia. It only requires one gene from one parent to develop. Within 12 to 18 months of the first symptom, the individual dies. There is ongoing research into the disease.
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