What's Wrong with the Transferrin?

A 2-year-old boy presented with developmental delay and rapidly progressing spasticity of lower limbs. A serum transferrin isoform test was requested as a work-up for congenital disorders of glycosylation (CDG). Figure 1 shows his serum transferrin isoelectric focusing pattern. Fig. 1. Lanes A–C, isoelectric focusing without neuraminidase; lanes D–F, isoelectric focusing after in vitro treatment of serum with neuraminidase. Lane A, normal serum; lane B, CDG type 1 patient; lane C, this patient; lane D, this patient; lane …