Features include always present findings: Type I transferrin isoform profile, Global developmental delay, and Intellectual disability; and common findings: Enlarged liver (hepatomegaly).

MAGT1 encodes magnesium transporter 1 (335 aa). Accessory component of the STT3B-containing form of the N-oligosaccharyl transferase (OST) complex which catalyzes the transfer of a high mannose oligosaccharide from a lipid-linked oligosaccharide donor to an asparagine residue within an Asn-X-Ser/Thr consensus motif in nascent polypeptide chains. Highest expression in Cells EBV-transformed lymphocytes (52.9 TPM) and Thyroid (52.7 TPM).

Congenital disorder of glycosylation, type ICC is associated with mutations in the MAGT1 gene on chromosome X.

The MAGT1 protein participates in MAGT1 transports Mg2+ from extracellular region to cytosol, TUSC3 transports Mg2+ from extracellular region to cytosol, and SLC41A1,2 transport Mg2+ from extracellular region to cytosol pathways.

MAGT1 is classified as a druggable target (Transporter category) with score 0.0.

Genetic testing for MAGT1 is available. Testing is considered confirmatory for diagnosis.

Phenotype severity distribution: 3 always present features, 1 common feature.