Spinal muscular atrophy: a motor neuron disorder or a multi-organ disease?

Authors

  • Monir Shababi,

    Corresponding author
    1. Department of Veterinary Pathobiology, Life Sciences Center, University of Missouri, Columbia, MO, USA
    2. Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri, Columbia, MO, USA
    • Correspondence

      Monir Shababi, Department of Veterinary Pathobiology, Life Sciences Center, University of Missouri, Room 404, Columbia, MO 65211, USA. T: + 1 573 8842680; F: + 1 573 8849395; E: ShababiM@missouri.edu

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  • Christian L. Lorson,

    1. Department of Veterinary Pathobiology, Life Sciences Center, University of Missouri, Columbia, MO, USA
    2. Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri, Columbia, MO, USA
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  • Sabine S. Rudnik-Schöneborn

    1. Institute of Human Genetics, Medical Faculty, University Hospital Aachen, Aachen, Germany
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Abstract

Spinal muscular atrophy (SMA) is an autosomal recessive disorder that is the leading genetic cause of infantile death. SMA is characterized by loss of motor neurons in the ventral horn of the spinal cord, leading to weakness and muscle atrophy. SMA occurs as a result of homozygous deletion or mutations in Survival Motor Neuron-1 (SMN1). Loss of SMN1 leads to a dramatic reduction in SMN protein, which is essential for motor neuron survival. SMA disease severity ranges from extremely severe to a relatively mild adult onset form of proximal muscle atrophy. Severe SMA patients typically die mostly within months or a few years as a consequence of respiratory insufficiency and bulbar paralysis. SMA is widely known as a motor neuron disease; however, there are numerous clinical reports indicating the involvement of additional peripheral organs contributing to the complete picture of the disease in severe cases. In this review, we have compiled clinical and experimental reports that demonstrate the association between the loss of SMN and peripheral organ deficiency and malfunction. Whether defective peripheral organs are a consequence of neuronal damage/muscle atrophy or a direct result of SMN loss will be discussed.

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