Neurodevelopmental profiles of 14 individuals with phosphomannomutase deficiency (PMM2‐CDG)

PMM2-CDG (formerly CDG-1a), the most common type of congenital disorders of glycosylation, is inherited in an autosomal recessive pattern. PMM2-CDG frequently presents in infancy with multisystemic clinical involvement, and it has been diagnosed in over 1000 people worldwide. There have been few natural history studies reporting neurodevelopmental characterization of PMM2-CDG. Thus, a prospective study was conducted that included neurodevelopmental assessments as part of deep phenotyping. This study, Clinical and Basic Investigations into Known and Suspected Congenital Disorders of Glycosylation (NCT02089789), included 14 participants (8 males and 6 females ages 2-33 years) with a confirmed molecular diagnosis of PMM2-CDG. Clinical features of PMM2-CDG in this cohort were neurodevelopmental disorders, faltering growth, hypotonia, cerebellar atrophy, peripheral neuropathy, movement disorders, ophthalmological abnormalities, and auditory function differences. All PMM2-CDG participants met criteria for intellectual disability (or global developmental delay if younger than age 5). The majority never attained certain gross motor and language milestones. Only two participants were ambulatory, and almost all were considered minimally verbal. Overall, individuals with PMM2-CDG present with a complex neurodevelopmental profile characterized by intellectual disability and multisystemic presentations. This systematic quantification of the neurodevelopmental profile of PMM2-CDG expands our understanding of the range in impairments associated with PMM2-CDG and will help guide management strategies.