Sialic acid content in serum IgG from patients with myotonic dystrophy compared with healthy controls.

One of the determinants of the lifetime of circulating glycoproteins is their content of the terminal carbohydrate sialic acid. In order to elucidate a possible mechanism behind reduced concentration of IgG in patients with myotonic dystrophy, serum IgG was isolated by affinity chromatography and its content of sialic acid determined. No difference between patients and healthy controls was found. The results provide further support to the idea that a host factor rather than an abnormality of the IgG molecule itself is responsible for the low concentration of serum IgG in this disease.