Primary Lateral Sclerosis

Primary Lateral Sclerosis is a topic covered in the 5-Minute Clinical Consult.

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  • Primary lateral sclerosis (PLS) is a rare progressive degenerative disease of the corticospinal and corticobulbar tracts (upper motor neurons [UMNs]), which spares the anterior horn cells.
  • Characterized by leg weakness, spasticity, and bulbar symptoms like dysphagia and dysarthria
  • Additional features include cognitive impairment, eye movement abnormalities, and urinary dysfunction.
  • Part of the spectrum of motor neuron diseases (MNDs) because some patients with PLS evolve to develop amyotrophic lateral sclerosis (ALS)
  • Conversion from PLS to ALS has been reported up to 27 years after the onset of spasticity.


  • Found in 1–3% of patients with motor neuron disorder
  • Onset is usually after age 40 years, although a juvenile form has been described.
  • Mean age at symptom onset is 54 years.
  • There is a slight male predominance, which is similar to ALS.

Incidence is difficult to determine due to rarity, misdiagnosis, and changing diagnosis. An estimated 1/10 million/year or 300 to 500 people in the United States are diagnosed yearly.

Estimated prevalence is 10 to 20/million.

Etiology and Pathophysiology

PLS is usually sporadic with no known cause; potential role of TAR DNA–binding protein 43 (TDP-43) (1)

  • Juvenile PLS and juvenile ALS has been correlated with a mutation in the ALS2 gene on chromosome 2. It is inherited in an autosomal recessive pattern.
  • Mutation of the ERLIN2 gene, a component of the endoplasmic reticulum lipid raft has been linked to juvenile PLS.

General Prevention

There is no known means of prevention.

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TY - ELEC T1 - Primary Lateral Sclerosis ID - 816019 ED - Baldor,Robert A, ED - Domino,Frank J, ED - Golding,Jeremy, ED - Stephens,Mark B, BT - 5-Minute Clinical Consult, Updating UR - PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -