MPS IIIa (N-sulfoglucosamine sulfohydrolase deficiency), MPS IIIb (α-N-acetylglucosaminidase deficiency), MPS IIIc (heparan α-glucosaminide N-acetyltransferase deficiency) and MPS IIId (N-acetylglucosamine-6-sulfatase deficiency) patients all display an altered degradation process of the glucosamine derivatives and should theoretically give rise to diagnostic dp1 NREs and possibly trisaccharides composed of glucosamine derivative-UA-glucosamine. The gene discussed is GNS; the disease is hyperinsulinemic hypoglycemia, familial, 4.