Sanfilippo syndrome

Alternative names  
Mucopolysaccharidosis type III (subtypes A - B - C - D); Heparan sulfate sulfatase deficiency (Type IIIA); N-acetylglucosaminidase deficiency (Type IIIB); Acetyl-CoA alpha-glucosaminide N-acetyltransferase deficiency (Type IIIC); N-acetylglucosamine-6-sulfate sulfatase deficiency (Type IIID)


Sanfilippo syndrome is one of the hereditary mucopolysaccharide storage diseases, which are characterized by the absence of one of several enzymes. Normally, these enzymes help rid the body of a substance found outside of our cells, called a mucopolysaccharide.

In Sanfilippo syndrome, large amounts of a mucopolysaccharide called heparan sulfate is excreted in the urine.

Causes, incidence, and risk factors

Sanfilippo syndrome is transmitted as an autosomal recessive trait. It is possibly the most common of the mucopolysaccharide storage diseases. In Sanfilippo syndrome, onset is relatively late, rather than during the first year of life.

As with most of the mucopolysaccharide storage diseases, affected individuals have coarse facial features, decreased mental development that progresses to severe mental retardation, stiff joints, gait disturbances, speech disturbances, and behavioral problems.

Unlike Hurler syndrome, in people with Sanfilippo syndrome, the cornea is clear, the condition is not as unrelenting, and survival times are longer, often into the 20s or later.



  • Family history of Sanfilippo syndrome

  • May have normal growth during first few years, but final height is below average

  • Delayed development followed by deteriorating mental status

  • Deterioration of gait

  • Coarse facial features

  • Full lips

  • Heavy eyebrows that meet in the middle of the face above the nose

  • Diarrhea

  • Stiff joints that may not extend fully

Signs and tests


  • Hepatomegaly (liver enlargement)

  • Spleen enlargement

  • Clear corneas

  • Echocardiogram may show thickened heart

  • Abnormal bone X-rays, such as thickened skull and oval vertebrae

  • Seizures, mental retardation

  • Activities of one of the enzymes listed in “Alternate Names” may be low in fibroblast skin cells

  • Urine may have increased heparan sulfate

  • Abnormal, pathological staining character of white blood cells called metachromasia

There is no specific treatment for Sanfilippo syndrome. Specific complications may respond to conventional treatments as they arise.

Support Groups
National MPS Society, Inc.,

Expectations (prognosis)

Severe retardation is the most important of the clinical problems. IQs may be below 50. Severe cases lead to death before 20 years of age.

In a minority of cases, Sanfilippo is compatible with a normal lifespan. The affected person may develop retinal degeneration leading to blindness, or may have seizures.



  • Blindness

  • Seizures

  • Mental retardation

  • Progressive neurologic disease leading to becoming wheelchair bound

  • Inability to care for self

Calling your health care provider
Call your health care provider if your child does not seem to be growing or developing normally.

Call for an appointment with your health care provider if you plan to have children and you have a family history of Sanfilippo syndrome.

Genetic counseling is recommended for prospective parents with a family history of Sanfilippo syndrome.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.