Hyperactivity, unexplained speech delay, and coarse facies--is it Sanfilippo syndrome?

Mucopolysaccharidosis-IIIB or Sanfilippo-B syndrome is caused by deficiency of lysosomal α-N-acetylglucosaminidase that leads to accumulation of heparan-sulphate and degeneration of central nervous system with progressive dementia, hyperactivity, and aggressive behavior. Mucopolysaccharidosis-III remains underdiagnosed as a cause of developmental delay and hyperactivity both in adults and children because in contrast to other mucopolysaccharidoses, they have little somatic disease, coarse facial features, hepatosplenomegaly or skeletal changes, and a high incidence of false-negative results on the urinary screening tests. We describe here a girl with the classic phenotype of mucopolysaccharidosis-IIIB to alert pediatricians to the possibility of this disorder in children with unexplained speech delay and hyperactivity and prevent unnecessary investigations.