CASE FILES: BIOCHEMISTRY
A N SW E R S TO C A SE 29: SA N F IL IP P O SY N D R O M E
A 6-year-old boy with severe mental retardation, family history of
mental retardation, language delays, and behavioral problems.
Diagnosis: Sanfilippo syndrome
Inheritance pattern: Autosomal recessive
Other causes: Hunter syndrome, Hurler syndrome, or Morquio syndrome
C L IN IC A L C O R R E L A T IO N
Excessive accumulation of proteins, nucleic acids, carbohydrates, and lipids
can result from deficiency of one or more lysosomal hydrolases. Lysosomal
storage diseases are classified by the stored material. Accumulation of gly-
cosaminoglycans results in mucopolysaccharidoses. Common causes of this
disorder include: Hunter syndrome, Hurler syndrome, and Sanfilippo syndrome.
Sanfilippo syndrome is inherited in an autosomal recessive pattern and clini-
cally evident by profound mental retardation, lack of normal developmen-
tal milestones, and significant language delay. Sanfilippo syndrome results
in an excess of heparan sulfate and can be caused by a variety of enzyme
A PPR O A C H TO L Y SO SO M A L D E G R A D A T IO N
O F G L Y C O SA M IN O G L Y C A N S
Describe how glycosaminoglycans and proteoglycans are synthesized.
Describe the biochemical pathways needed for glycosaminoglycan
Explain why lysosomal enzyme deficiencies and glycosaminoglycan
accumulation result in clinical signs/symptoms.
Endoglycosidase: An enzyme that hydrolyzes an interior glycosidic bond
between two sugars in a polysaccharide or oligosaccharide to produce
two smaller oligosaccharides.
Exoglycosidase: An enzyme that hydrolyzes the glycosidic bond between
the terminal two sugars of an oligo- or polysaccharide releasing the ter-
minal sugar from the nonreducing end of the polymer, leaving it one