Editing Pelizaeus–Merzbacher disease (section)

==Signs and symptoms==
The hallmark signs and symptoms of Pelizaeus–Merzbacher disease include little or no movement in the arms or legs, respiratory difficulties, and characteristic horizontal movements of the eyes left to right.{{citation needed|date=September 2020}}

The onset of Pelizaeus–Merzbacher disease is usually in early infancy. The most characteristic early signs are [[pathologic nystagmus|nystagmus]] (rapid, involuntary, rhythmic motion of the eyes) and [[hypotonia|low muscle tone]].  Motor abilities are delayed or never acquired, mostly depending upon the severity of the mutation. Most children with Pelizaeus–Merzbacher disease learn to understand language, and usually have some speech. Other signs may include [[tremor]], lack of coordination,  involuntary movements, weakness, unsteady [[gait]], and over time, spasticity in legs and arms.  [[Muscle contracture]]s often occur over time. Mental functions may deteriorate. Some patients may have [[convulsions]] and skeletal deformation, such as [[scoliosis]], resulting from abnormal muscular stress on bones.<ref>{{Cite web |title=Pelizaeus-Merzbacher disease: MedlinePlus Genetics |url=https://medlineplus.gov/genetics/condition/pelizaeus-merzbacher-disease/ |access-date=2022-06-25 |website=medlineplus.gov |language=en}}</ref>