The second DDOST-CDG patient with lactose intolerance, developmental delay, and situs inversus totalis.

Congenital disorders of glycosylation (CDGs) are inherited metabolic diseases affecting protein and lipid glycosylation. DDOST-CDG is a rare, newly identified type of CDGs, with only one case reported so far. In this study, we report a Chinese patient with a homozygous pathogenic variant in DDOST (c.1187G>A) and who presented with feeding difficulty, lactose intolerance, facial dysmorphism, failure to thrive, strabismus, high myopia, astigmatism, hypotonia, developmental delay and situs inversus totalis. Serum transferrin isoelectrofocusing demonstrated defective glycosylation in our patient. This finding further identifies DDOST as a genetic cause of CDGs and expands the clinical phenotype of DDOST-CDG.