| Image = | Caption = | DiseasesDB = | ICD10 = | ICD9 = | ICDO = | OMIM = | MedlinePlus = | eMedicineSubj = | eMedicineTopic = | MeshName = Juvenile+Primary+Lateral+Sclerosis | MeshNumber = | }}Juvenile primary lateral sclerosis (JPLS) ,also known as as primary lateral sclerois (PLSJ), is a rare genetic disorder, with a small number of reported cases, 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 and progression Symptoms of JPLS 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 we