Identification through exome sequencing of the first PMM2-CDG individual of Mexican mestizo origin.

Congenital Disorders of Glycosylation (CDG) are scarcely reported from Latin America. We here report on a Mexican mestizo with a multi-systemic syndrome including neurological involvement and a type I transferrin (Tf) isoelectric focusing (IEF) pattern. Clinical exome sequencing (CES) showed known compound missense variants in PMM2 c.422G > A (p.R141H) and c.395 T > C (p.I132T), coding for the phosphomanomutase 2 (PMM2). PMM2 catalyzes the conversion of mannose-6-P to mannose-1-P required for the synthesis of GDP-Man and Dol-P-Man, donor substrates for glycosylation reactions. This is the third reported Mexican CDG patient and the first with PMM2-CDG. PMM2 has been recently identified as one of the top 10 genes carrying pathogenic variants in a Mexican population cohort.