About Facioscapulohumeral Muscular Dystrophy (FSHD)
FSHD is a rare genetic myopathy in which immune cells invade diseased skeletal muscle and for which there are no approved treatments. The primary clinical phenotype of FSHD is debilitating skeletal muscle deterioration and weakness. The symptoms of FSHD often appear early in the face, shoulder blades, upper arms, lower legs and trunk, and can affect certain muscles while adjacent muscles remain healthy. In addition to muscle weakness, FSHD patients often experience debilitating fatigue and chronic pain.
While estimates of FSHD prevalence vary, studies exploring the topic have identified average prevalence rates of approximately one in 17,000. Applying this rate to the U.S. population, as of November 1, 2014, yields a domestic FSHD population of approximately 19,000.
There are currently no approved treatments for FSHD. The standard of care in management of the disease includes physical therapy and, in the presence of severe muscle weakness, orthotic devices or surgical interventions may be needed to maintain musculoskeletal stability.
While FSHD can manifest at any age, the onset of symptoms in many patients occurs before the age of 18. We refer to this patient population as early onset FSHD. Within the early onset population are individuals with symptom onset at less than five years of age, with progression in disease prior to age ten. These individuals have the most severe muscle symptoms and significant extra-muscular manifestations such as auditory deficits and retinal complications that may result in vision loss. This sub-group of early onset patients are often referred to as having “infantile onset” FSHD.
Estimates of prevalence vary, however we believe the domestic “infantile onset” FSHD population is approximately 1,000.
Limb-Girdle Muscular Dystrophy 2B (LGMD2B)
Limb-girdle muscular dystrophy (LGMD), a group of uniformly progressive muscular dystrophies characterized predominantly by proximal weakness affecting the pelvic and shoulder girdles and usually sparing the face. This group of disorders, recently re-classified based on the genetic underpinnings of diseases, are categorized by inheritance pattern: dominantly inherited forms (i.e., LGMD1) and those with recessively-inherited forms (i.e., LGMD2B).
The age of onset, severity, and features of LGMD vary among the subtypes. Overall LGMD affects men and women equally. LGMD patients typically suffer from skeletal muscle weakness, immune cell invasion and skeletal muscle deterioration all in identifiable, specific muscles.
There are multiple lines of evidence supporting a prominent role of inflammation in the pathophysiology of LGMD2B. Patients with LGMD2B possess a dysregulated immune response, including immune cell infiltration into affected muscle, increased expression of pro-inflammatory cytokines and altered cellular responses.
Based on a prevalence rate of 1:20,000, we estimate that LGMD affects an estimated 16,000 patients in the U.S., approximately 3,000 of whom have LGMD2B.
No definitive treatments exist for LGMD2B.