Renal involvement in PMM2-CDG, a mini-review

Phosphomannomutase 2 deficiency (PMM2-CDG) is the most common N-linked glycosylation disorder. The majority of patients present with a multisystem phenotype, including central nervous system involvement, hepatopathy, gastrointestinal and cardiac symptoms, endocrine dysfunction and abnormal coagulation. Renal abnormalities including congenital malformations and altered renal function are part of the multisystem manifestations of congenital disorders of glycosylation. We reviewed the literature on 933 patients with molecularly and/or enzymatically confirmed PMM2 deficiency to evaluate the incidence of renal involvement in PMM2-CDG. Renal abnormalities were reported in 56 patients. Congenital abnormalities were present in 41 out of these 55. Cystic kidney and mild proteinuria were the most common findings. One of the most severe renal manifestations, congenital nephrotic syndrome, was detected in 6 children. Renal manifestations were not associated with the presence of specific PMM2 alleles. This review summarizes the reported renal abnormalities in PMM2-CDG and draws attention to the pathophysiological impact of abnormal glycosylation on kidney structure and function.