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Early diagnosis is critical for the management of MPS IIIA, yet delayed or missed diagnoses are common1

Many children with MPS IIIA experience a prolonged journey to diagnosis, often as the result of being misdiagnosed with other developmental disorders with overlapping clinical presentations.1

Relatively mild or absent symptomatology early in the disease course and the lack of inclusion of MPS IIIA in newborn screening programs may also contribute to the diagnostic challenge1; however, up to 68% of children with MPS IIIA develop initial symptoms within the first year of life.2

Diagnostic delay icon
The median diagnostic delay* was ~3 years in a study of children with MPS III3
*Defined as the time between the first medical specialist visit and final diagnosis of MPS III.3
Age of diagnosis icon
The median age at diagnosis was ~5 years in a study of children with MPS III3
Misdiagnosis icon
MPS IIIA is commonly misdiagnosed as other developmental disorders2
  • Autism spectrum disorder
  • Attention-deficit/hyperactivity disorder (ADHD)
  • Idiopathic developmental delay

Urinary GAG analysis can screen for MPS IIIA, but diagnosis is confirmed using genetic testing and/or enzyme activity assay1

SCREENING1,4
Urinary GAG screening icon
Urinary GAG Screening1,4
  • Cannot rule out diagnosis due to poor sensitivity and high rates of false negatives
  • Abnormal/negative results with clinical suspicion of MPS are confirmed via genetic testing and/or enzyme activity assay
DIAGNOSIS1,5
Genetic testing icon
Genetic Testing
  • Identifies pathogenic variants in SGSH1,5
AND / OR
Enzyme Activity Assay icon
Enzyme Activity Assay5
  • Measures the activity of all 4 enzymes associated with MPS III
  • Very low or absent activity of sulfamidase, with normal activity of the other 3 MPS III enzymes, confirms an MPS IIIA diagnosis
Screening of family members and prenatal testing to determine carrier status

In families with individuals living with MPS IIIA, screening of additional family members and prenatal testing can be performed to determine carrier status.1

Discover how MPS IIIA is managed

Abbreviations: GAG, glycosaminoglycan; MPS, mucopolysaccharidosis; MPS IIIA, mucopolysaccharidosis type IIIA.

References

  1. Muschol N, Giugliani R, Jones SA, et al. Sanfilippo syndrome: consensus guidelines for clinical care. Orphanet J Rare Dis. 2022;17(1):391.
  2. Escolar ML, Bradshaw J, Byers VT, et al. Development of a clinical algorithm for the early diagnosis of mucopolysaccharidosis III. J Inborn Errors Metab Screen. 2020;8:e20200002.
  3. Kuiper GA, Meijer OLM, Langereis EJ, et al. Failure to shorten the diagnostic delay in two ultra-orphan diseases (mucopolysaccharidosis types I and III): potential causes and implications. Orphanet J Rare Dis. 2018;13(1):2.
  4. Bodamer OA, Giugliani R, Wood T, et al. The laboratory diagnosis of mucopolysaccharidosis IIIB: a changing landscape. Mol Genet Metab. 2014;113(1-2):34-41.
  5. Wagner VF, Northrup H. Mucopolysaccharidosis type III. 2019. In: Adam MP, Feldman J, Mirzaa GM, et al, eds. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024. Accessed January 2, 2025. https://www.ncbi.nlm.nih.gov/books/NBK546574/