Primary Lateral Sclerosis (PLS)

Primary lateral sclerosis (PLS) is a progressive neuromuscular (nerves and muscles) condition that causes worsening muscle weakness and/or stiffness. Symptoms usually begin in your legs. Over time, weakness and stiffness spread to other muscles throughout your body.

Because there’s no cure for PLS, treatment focuses on managing your symptoms and providing mobility support like using a cane or a walker.

How common is PLS?

PLS is rare. The exact rate of occurrence is unknown.

PLS vs. ALS: What’s the difference?

Both primary lateral sclerosis (PLS) and amyotrophic lateral sclerosis (ALS) are neuromuscular conditions. There are differences between each.

Can PLS turn into ALS?

Early signs of ALS can look like PLS. PLS only affects your upper motor neurons (UMN) and ALS affects both your upper and lower motor neurons (LMN). You may receive a PLS diagnosis first if you only have symptoms that affect your UMN. Later, symptoms of ALS in both your UMN and LMN become apparent, so your healthcare provider may change your diagnosis to ALS.

Most cases that look like PLS are actually early stages of UMN-predominant ALS that eventually develop into ALS. For this reason, a diagnosis of PLS should only be made after you experience symptoms for at least three to four years.