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Genetic and Rare Diseases Information Center (GARD)

Primary lateral sclerosis

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What are the signs and symptoms of Primary lateral sclerosis?

Primary lateral sclerosis (PLS) causes weakness in the voluntary muscles, such as those used to control the legs, arms and tongue. PLS can happen at any age, but it is more common after age 40. A subtype of PLS, known as juvenile primary lateral sclerosis, begins in early childhood. PLS is often mistaken for another, more common motor neuron disease called amyotrophic lateral sclerosis (ALS). However, primary lateral sclerosis progresses more slowly than ALS, and in most cases is not considered fatal.[1]

Signs and symptoms of PLS typically take years to progress.[1] The hallmark of PLS is progressive weakness and spasticity of voluntary muscles. The first symptoms are often tripping or difficulty lifting the legs. Other people may be the first to notice a change in the affected person's gait. Occasionally, speaking (dysarthria) and swallowing (dysphasia) difficulties, or arm weakness are the first symptoms. Speech problems can begin with hoarseness, a reduced rate of speaking, excessive clearing of the throat, or slurred speech when a person is tired. In some cases, speech becomes so slurred that others cannot understand it. Drooling can be a problem as well due to weakened bulbar muscles.[2] Many people report painful muscle spasms and other pain. Other common symptoms may include hyperactive reflexes and Babinkski's sign. Wherever symptoms originate, the legs, arms, hands, and speech and swallowing muscles are eventually affected. As the disease progresses, assistive devices such as canes, walkers or wheelchairs are typically needed.[2]
Last updated: 3/30/2011

The Human Phenotype Ontology provides the following list of signs and symptoms for Primary lateral sclerosis. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms.

Signs and Symptoms Approximate number of patients (when available)
Abnormal upper motor neuron morphology -
Adult onset -
Autosomal dominant inheritance -
Babinski sign -
Dysphagia -
Hyperreflexia -
Slow progression -
Spastic dysarthria -
Spastic gait -
Spastic tetraparesis -

Last updated: 11/1/2015

The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature.

The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined.

Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.

  1. Primary lateral sclerosis (PLS). Mayo Clinic. October 16, 2010; Accessed 3/30/2011.
  2. John Fink. About PLS (Primary Lateral Sclerosis). Spastic Paraplegia Foundation. 2011; Accessed 3/30/2011.

See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.