Abstract
Mucopolysaccharidosis Type IIIA (MPS IIIA) or Sanfilippo-A syndrome is caused by a deficiency in lysosomal a-heparan N-sulfatase. Its clinical manifestations include progressive dementia, hyperactivity, and aggressive behavior. Unlike other mucopolysaccharide disorders, the diagnosis of MPS IIIA is challenging in both adults and children. This diagnostic challenge has been associated with the high incidence of false negative results encountered on urinary screening tests. We herein describe Sanfilippo-A syndrome in a pediatric patient who presented with progressive hyperactivity, delayed language, and developmental delay and a negative urine screening test. We emphasized that these findings may serve as possible initial presentations of MPS IIIA; therefore, screening for MPS should be done in all patients with unexplained psychomotor retardation and progressive hyperactivity.