Objectives To investigate motor function associations with age, sex, and D4Z4 repeats among participants with early-onset facioscapulohumeral muscular dystrophy (FSHD) type 1 as defined by weakness onset before 10 years of age. Methods We collected standardized motor assessments, including manual muscle testing (MMT), quantitative muscle testing, functional motor evaluations, and clinical severity scores (CSSs), at 12 Cooperative International Neuromuscular Research Group centers. To measure associations, we used linear regression models adjusted for sex, evaluation age, age at onset of weakness, and D4Z4 repeats. Results Among 52 participants (60% female, mean age 22.9 ± 14.7 years), weakness was most pronounced in the shoulder and abdominal musculature. Older enrollment age was associated with greater CSSs (p = 0.003). When adjusted for enrollment age, sex, and D4Z4 repeats, younger age at onset of facial weakness was associated with greater CSSs, slower velocities in timed function tests, and lower MMT scores (p < 0.05). Conclusion Significant clinical variability was observed in early-onset FSHD. Earlier age at onset of facial weakness was associated with greater disease severity. Longitudinal assessments are needed to determine the rate of disease progression in this population.
Bibliographical noteFunding Information:
Funded by the FSH Society (grant FSHS-02010-04), Muscular Dystrophy Canada, and the FSHD Global Research Foundation.
The authors thank the participants and families for their support, the FSH Society for provision of a travel grant for study participants, Dr. Kathryn Wagner and Dr. Rabi Tawil for their helpful advice, the National Registry of FSHD at the University of Rochester for help with patient recruitment, and Dr. Yoram Nevo for reviewing the manuscript. The authors take full responsibility for the contents of this manuscript, which do not represent the views of the Department of Veterans Affairs or the US Government.
This study was funded by the FSH Society, Muscular Dystrophy Canada, and the FSHD Global Research Foundation. The authors report no competing interests. Go to Neurology.org/N for full disclosures.
© 2018 American Academy of Neurology.