Digital Biotyping of FSHD Patients and Controls

Facioscapulohumeral muscular dystrophy (FSHD) is a devastating progressive muscle dystrophy. There is no treatment. FSHD is generally characterized by asymmetrical weakness and wasting of facial, shoulder girdle and upper arm muscles followed by weakness of muscles of the trunk and lower extremities, but disease severity varies widely between patients. Relatively long periods of stability are interspersed with short periods of potentially steep decline, leading overall to a slow but unpredictable rate of progression. Different genotypes underlying FSHD have been identified, but they result in highly similar phenotypes and at the molecular level converge on undue expression of the transcription factor, DUX4, in skeletal muscle, which is thought to (ultimately) lead to muscle wasting due to inflammation, apoptosis, and oxidative stress. There is no approved treatment, although various companies are engaged in FSHD drug discovery and development aimed in particular at reducing DUX4 expression. Multiple treatment options are currently under development in both preclinical and early clinical stages. However, these efforts face significant challenges in the path to regulatory approval. Because of the slow and variable rate of progression of FSHD, evidencing a significant treatment response will be cumbersome using only the existing measurements of muscle function. The successful development of these investigative treatments for FSHD is therefore highly dependent on the availability of validated disease and treatment biomarkers to monitor disease progression and response to treatment, respectively. To date, no such validated biomarkers exist. This study is important for four reasons: 1. Clinical testing of FSHD drug candidates requires the availability of clinical biomarkers that (a) change relatively rapidly over time; (b) allow for identification of fast progressors; and (c) correlate with "gold standard", but slowly changing, clinical severity and/or functional scores.