Mucopolysaccharidosis type 3 (Sanfilippo)
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A child with normal appearance develops severe behavioral problems, sleep disturbance, and progressive dementia. Mild coarse features develop later.
AR; 4 subtypes (A-D) with different enzymes
- Predominantly CNS disease
- Severe behavioral problems, sleep disturbance
- Mild somatic features (coarse features, hepatosplenomegaly less prominent)
- Heparan sulfate elevated
- Urine glycosaminoglycans: isolated elevation of heparan sulfate (distinguishes from other MPS types)
- Subtype determined by deficient enzyme activity: A (SGSH, heparan-N-sulfatase), B (NAGLU), C (HGSNAT), D (GNS)
- Molecular confirmation of the relevant gene
- No disease-modifying therapy approved; supportive and symptomatic care
- Manage behavioral problems and sleep disturbance (CNS-predominant disease limits the benefit of enzyme replacement, which does not cross the blood-brain barrier)
- Anticonvulsants for seizures; multidisciplinary developmental, neurologic, and palliative support
"SanfIIIppo": the Roman numeral III is hidden in the name. MPS III is primarily a neurological disorder, with profound neurodegeneration by age 6-10 years and relatively mild somatic features.
4 enzymes, 1 phenotype: Sanfilippo has 4 subtypes (A-D), each caused by a different enzyme deficiency, but all share the same clinical presentation (primarily CNS disease with behavioral problems and hyperactivity).