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Disease Profile

Juvenile 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 / 1 000 000

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)

JPLS; Primary lateral sclerosis, juvenile; PLS juvenile


Congenital and Genetic Diseases; Nervous System Diseases


Juvenile primary lateral sclerosis is a rare disorder characterized by progressive weakness and stiffness of muscles in the arms, legs, and face. This disorder damages motor neurons, which are specialized nerve cells in the brain and spinal cord that control muscle movement. Symptoms begin in early childhood and progress over a period of 15 to 20 years. Juvenile primary lateral sclerosis is caused by mutations in the ALS2 gene. It is inherited in an autosomal recessive pattern.[1]


Juvenile primary lateral sclerosis is a rare disorder characterized by progressive weakness and stiffness of muscles in the arms, legs, and face. Symptoms of juvenile primary lateral sclerosis begin in early childhood and progress over a period of 15 to 20 years. Early symptoms include clumsiness, muscle spasms, weakness and stiffness in the legs, and difficulty with balance. As symptoms progress, they include weakness and stiffness in the arms and hands, slurred speech, drooling, difficulty swallowing, and an inability to walk.[1]

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 pyramidal sign
Abnormal upper motor neuron morphology
Abnormal shape of upper motor neuron
Gait imbalance
Abnormality of balance
Abnormality of equilibrium
Imbalanced walk

[ more ]

Increased reflexes
Muscle weakness
Muscular weakness
Pseudobulbar behavioral symptoms
Spastic gait
Spastic walk
Spastic tetraparesis
30%-79% of people have these symptoms
Poor swallowing
Swallowing difficulties
Swallowing difficulty

[ more ]

Loss of speech
Spastic dysarthria
5%-29% of people have these symptoms
Abnormality of the bladder
Sensory neuropathy
Damage to nerves that sense feeling
Skeletal muscle atrophy
Muscle degeneration
Muscle wasting

[ more ]

Percent of people who have these symptoms is not available through HPO
Autosomal recessive inheritance
Babinski sign
Cerebral cortical atrophy
Decrease in size of the outer layer of the brain due to loss of brain cells
Childhood onset
Symptoms begin in childhood
Difficulty in tongue movements
Juvenile onset
Signs and symptoms begin before 15 years of age
Saccadic smooth pursuit
Slow progression
Signs and symptoms worsen slowly with time
Spasticity of facial muscles
Spasticity of pharyngeal muscles


Juvenile primary lateral sclerosis is caused by mutations in the ALS2 gene. The ALS2 gene provides instructions for making a protein called alsin. Alsin is abundant in motor neurons, but its function is not fully understood. Mutations in the ALS2 gene alter the instructions for producing alsin. As a result, alsin is unstable and decays rapidly, or it is disabled and cannot function properly. It is unclear how the loss of functional alsin protein damages motor neurons and causes juvenile primary lateral sclerosis.[1]


Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

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

  • Genetics Home Reference (GHR) contains information on Juvenile primary lateral sclerosis. This website is maintained by the National Library of Medicine.

In-Depth Information

  • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
  • 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 Juvenile primary lateral sclerosis. Click on the link to view a sample search on this topic.


  1. Juvenile primary lateral sclerosis. Genetics Home Reference (GHR). 2007; https://ghr.nlm.nih.gov/condition/juvenile-primary-lateral-sclerosis. Accessed 3/4/2011.

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