Updated: 3/11/2018

Facioscapulohumeral Muscular Dystrophy

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Introduction
  • A neuromuscular disorder which causes progressive muscle weakness in the face (facio), shoulder girdle (scapulo), and upper arm (humeral)
  • Epidemiology
    • incidence
      • third most common muscular dystrophy after Duchenne and myotonic dystrophy
      • 1 in 14,000 births
    • prevalence 
      • 2 to 7 per 100,000 individuals
    • demographics
      • male = female
      • males more severely affected
      • 95% present prior age of 20
  • Genetics
    • inheritance pattern
      • autosomal dominant (majority)
      • up to 30% of mutations can be spontaneous
    • mutation
      • deletion of repeated elements of D4Z4 on chromosome 4q35
      • double homeobox 4 (DUX4) no longer supressed 
        • believed to cause disease through gain-of-function mechanism
  • Associated Conditions
    • orthopaedic manifestations
      • scoliosis (rare)
      • camptocormia (bent spine syndrome)
  • Prognosis
    • insidious disease course
    • ~ 20% of patients > 50 years or older require a wheelchair
    • life expectancy is NOT shortened
 
Classification
  • Type 1A (FSHD1A)
    • most common form
    • also referred to as chromosome 4 linked
  • Type 1B (FSHD1B)
    • rare
    • also referred to as non-chromosome 4 linked
  • Infantile
    • more severe subtype of Type 1A and 1B and symptoms present earlier (~ 5 years old)
    • most patients become wheelchair bound during the 2nd decade of life
    • marked lumbar lordosis is progressive and is pathognomonic for infantile FSHD 
    • hearing loss, vision problems and seizures have been documented
    • have severely compromised pulmonary function and succumb in early adolescence
Presentation
  • Symptoms
    • slow muscular weakness over time
  • Physical Exam
    • inspection
      • scapular winging with limited arm abduction
        • causing prominent shoulder blades
      • incomplete eye closure
      • transverse smile
      • absence of eye and forehead wrinkles
      • selective sparing of deltoid, distal part of pectoralis major, and erector spinae muscles
    • motion
      • marked decrease in shoulder flexion and abduction
Imaging
  • Radiographs
    • do not play an important role in evaluation or treatment
Studies
  • Labs
    • CPK levels usually normal
  • Electrodiagnostic
    • EMG usually shows nonspecific myopathic changes with fibrillations
  • Muscle Biopsy
    • nonspecific chronic myopathic changes
    • performed only in those individuals in whom FSHD is suspected but not confirmed by molecular genetic testing
  • Genetic Testing
    • 95% sensitive and highly specific for FSHD
  • Pulmonary Function Testing
    • baseline testing at diagnosis
    • once disease has progressed to include proximal lower extremities PFTs should be done yearly
Treatment
  • Nonoperative
    • PT/OT, speech therapy
      • indications
        • shoulder girdle and upper arm weakness
          • to maintain strength and range of motion of affected muscles
      • outcomes
        • although their arms become gradually weaker from adolescence on, patients can usually work into later life
  • Operative
    • scapulothoracic fusion
      • indications
        • scapular winging
      • technique
        • wiring of the medial border of the scapula to ribs three through seven
        • internal fixation is achieved with 16-gauge wire
        • wires ensure firm fixation and eliminate the need for postoperative immobilization and subsequent rehabilitation
        • child uses a sling for 3 to 4 days postoperatively, and then begins a physical therapy program
      • outcomes
        • increased active abduction and forward flexion of the shoulder, and improved function as well as cosmesis
Complications
  • The following complications have been reported following scapulothoracic fusion:
    • Infection
    • Pneumothorax
    • Nonunion
    • Failure of Fixation
 

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