An organized, planned and comprehensive collection of data on individuals with PLGD and their family members is needed to address the knowledge gaps in PLGD. A single country registry is limited in value as the number of people affected in a single country is low, and likely will fail to identify the full spectrum of the disorder. Therefore, an international retrospective/prospective study has been initiated to gain broad insights into the disease, its progression and optimal treatment, and to develop severity categories that could be used to assist in disease course prediction.