Approximately 10,000, or 1.1 per 100,000 people in the world, are estimated to be living with TTR-FAP, which often shows up when patients are in their thirties or forties. TTR-CM tends to affect older males, ie., men who are 65 or older.
However, many cases of both forms of the disease are never diagnosed, or are mistaken for other diseases, so it is likely that more people have this disease. As awareness of the condition increases, and patient diagnosis improves, the medical community will have a better idea of how many people suffer from both forms of this rare disease.
Both forms of the disease are caused by a genetic mutation. TTR-FAP results from over 100 different mutations in the TTR gene that cause protein misfolding. Only one mutant gene is needed to transmit the disease, and an affected parent has a 50% chance of passing the mutation on to his or her children.