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Disease Profile

Primary lateral sclerosis

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

1-9 / 100 000

US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Adult-onset PLS; Adult-onset primary lateral sclerosis


Congenital and Genetic Diseases; Nervous System Diseases


Primary lateral sclerosis (PLS) is a rare neuromuscular disease that affects the nerve cells that control the voluntary muscles. Problems in the legs (such as weakness, stiffness, spasticity, and balance problems) are often observed first, but hand clumsiness and changes in speech can be early symptoms, as well. The condition is progressive (gradually becomes worse over time); however, affected people have a normal life expectancy. The underlying cause of adult PLS is currently unknown. In most cases, it occurs sporadically in people with no family history of the condition. A subtype of PLS, called juvenile PLS, is caused by changes (mutations) in the ALS2 gene and is inherited in an autosomal recessive manner. Treatment is based on the signs and symptoms present in each person.[1][2][3]


The signs and symptoms of primary lateral sclerosis (PLS) often develop between the ages of 40 and 60 and progress (become worse) over time. The voluntary muscles of the legs are often involved first, with symptoms beginning in one leg and then progressing to the other. In general, people with PLS may experience:[1][2][3]

  • Muscle weakness
  • Muscle stiffness and spasticity
  • Difficulty with balance and clumsiness
  • Slowed movement
  • Problems with speech

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Abnormal upper motor neuron morphology
Abnormal shape of upper motor neuron
Babinski sign
Generalized hyperreflexia
30%-79% of people have these symptoms
Poor swallowing
Swallowing difficulties
Swallowing difficulty

[ more ]

EMG: chronic denervation signs
Loss of speech
Progressive spastic paraparesis
Pseudobulbar signs
Spastic dysarthria
Spastic gait
Spastic walk
5%-29% of people have these symptoms
Cervical spinal cord atrophy
Motor axonal neuropathy
Percent of people who have these symptoms is not available through HPO
Adult onset
Symptoms begin in adulthood
Autosomal dominant inheritance
Increased reflexes
Slow progression
Signs and symptoms worsen slowly with time
Spastic tetraparesis


A diagnosis of primary lateral sclerosis (PLS) may be suspected based on the presence of characteristic signs and symptoms. Several different medical tests may then be ordered to confirm the diagnosis and rule out other conditions (such as multiple sclerosis and amyotrophic lateral sclerosis) that can be associated with similar features. These tests may include:[1][2]

Although a preliminary diagnosis of PLS can be made after other conditions are ruled out, it may take repeated testing over three to four years to confirm the diagnosis.[1]


The treatment of primary lateral sclerosis (PLS) is based on the signs and symptoms present in each person. For example, certain medications may be prescribed to treat the muscle stiffness and/or pain that can be associated with the condition. Physical therapy and occupational therapy can help maintain muscle strength, flexibility and range of motion, and may prevent joint immobility. Assistive devices such as braces, canes, walkers or wheelchairs may be needed for continued mobility. Speech therapy may be recommended when facial muscles are involved.[1][2][3]


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Learn more

    These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

    Where to Start

      In-Depth Information

      • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
      • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
      • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
      • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
      • PubMed is a searchable database of medical literature and lists journal articles that discuss Primary lateral sclerosis. Click on the link to view a sample search on this topic.


        1. Primary lateral sclerosis (PLS). Mayo Clinic. October 2016; https://www.mayoclinic.org/diseases-conditions/primary-lateral-sclerosis/symptoms-causes/dxc-20214456.
        2. Carmel Armon, MD, MSc, MHS. Primary Lateral Sclerosis. Medscape Reference. December 2015; https://emedicine.medscape.com/article/1171782-overview.
        3. Primary Lateral Sclerosis Information Page. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/All-Disorders/Primary-Lateral-Sclerosis-Information-Page. Accessed 4/13/2017.

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