Results
The summation of findings among the study population demonstrated that
the presenting symptoms, developmental milestones achieved, and
progression of symptoms reported are consistent with many previous
studies of patients with PLP1 duplications. All patients
exhibited onset within the first year of life, with nystagmus
predominating as the first symptom noticed. All patients exhibited
delays in both motor and language development; however, many individuals
were able to meet several developmental milestones. They exhibited some
degree of continued motor impairment with none having the ability to
walk independently. All patients were able to complete at least some of
the cognition achievements and although not all were verbal, a number
were able to use communication devices to complete these tasks. A
critical tool of the study was the functional disability scale which
provided a major advantage in helping quantify the clinical course of
PMD, and for several, we were able to gather this information at more
than one point in time. These reported findings in our cohort contribute
important insight into the clinical heterogeneity and potential
underlying mechanisms that define the molecular pathogenesis of the
disease.