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Updated: Jun 15 2021

Facioscapulohumeral Muscular Dystrophy

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  • summary
    • Facioscapulohumeral Muscular Dystrophy is a common congenital neuromuscular disorder which causes progressive muscle weakness in the face, shoulder girdle, and upper arm.
    • Diagnosis is made clinically with presence of a combination of scapular winging with limited arm abduction, incomplete eye closure, transverse smile, absence of eye and forehead wrinkles, with selective sparing of deltoid, distal part of pectoralis major, and erector spinae muscles.
    • Treatment is usually physical and occupational therapy. Operative scapulothoracic fusion is indicated for scapular winging associated with progressive pain.  
  • 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
  • Etiology
    • 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)
  • 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
  • Prognosis
    • Insidious disease course
      • ~ 20% of patients > 50 years or older require a wheelchair
    • Life expectancy is NOT shortened
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