The mean duration was 16 years with the longest one being 47 years (chart 3.5), which is compatible to the research of Ngo Minh Vinh (37, 1 ± 14, 4 years) and the youngest patient was 16 years old. Our results are also equivalent to Reich and Ruiz's research with the mean age of onset being 35 and 36.2 years old, respectively.