A rare disease is any disease that affects a small percentage of the population (e.g., 5 people in 10,000 in Europe or less than 200,000 people in United States of America).
Metabolic diseases consist of diseases or disorders that disrupt normal metabolism, i.e. the process of converting food into energy at a cellular level.
Metabolic diseases affect the body ability to perform critical biochemical reactions involving the processing or transportation of proteins (amino acids), carbohydrates (sugars and starches), and/or lipids (fatty acids).
Metabolic diseases are rare, but they are not that uncommon when considered all together. As a group, it is estimated that metabolic disorders affect approximately 1 in 1,000 individuals.
Metabolic diseases are typically hereditary, yet some people affected by them may appear healthy for days, months, or even years.