Werdnig-Hoffmann disease

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Werdnigg-Hoffman is the most severe form of Spinal Muscular Atrophy (SMA). Progressive loss of brainstem and spinal motor neurones results in worsening weakness.

  • Also known as Spinal Muscular Atrophy type I and previously Infantile Spinal Muscular Atrophy.


See also the associated article: Spinal Muscular Atrophy.


Aetiology

Lower motor neurones only are affected in Wernig-Hoffman. Progressive destruction results in weakness and reduced movements.

  • An abnormal 'Survival Motor Neurone' (SMN) gene has been implicated.


Clinical Features and Diagnosis

Progressive weakness and reduced movement are the primary features, sometimes evident in-utero.

  • Reduced foetal movement (final trimester)
  • Hypotonia in all muscle groups
    • Never able to sit upright
  • Impaired swallow / feeding
  • Respiratory impairment
  • Weak cry
  • Reduced reflexes / areflexia


Diagnosis is based on clinical suspicion

  • EMG: Denervation and fibrillation
  • Creatinine-Kinase: normal or elevated
  • SMN gene mutation


Treatment and Prognosis

Prognosis is poor. Multidisciplinary supportive treatment is required, including genetic counselling.

  • 95% mortality at 18 months
  • Mechanism of death is commonly due to respiratory impairment or infections.


See also the associated article: Spinal Muscular Atrophy.

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