Results
Sixteen subjects/parents or guardians completed the medical history questionnaire (MHQ) and medical record requests (See Table 1). The average age of the study subject at the time of completion was 22 years (range 7 to 48 years). Sixteen subjects had at least one functional disability scale score available. The average age at which the first functional disability scale (FDS1) score was obtained was 19 years (range 7 to 42 years; standard deviation 10.7 years). Nine of those individuals had at least two functional disability scale scores available. The average age at which the second functional disability scale (FDS2) score was obtained was 29 years (range from 14 to 48 years). The average number of years of follow-up from FDS1 to FDS2 was 5.4 years (range 4 to 7 years). Two individuals had a third functional disability scale score available. The average age at which the third functional disability scale (FDS3) score was obtained was 48.5 years (range 46 to 51 years). The average number of years of follow-up from FDS2 to FDS3 was 5.5 years. In total, three sibling pairs were included in this study.