Mucopolysaccharidosis type III (Sanfilippo syndrome) and misdiagnosis of idiopathic developmental delay, attention deficit/hyperactivity disorder or autism spectrum disorder

Abstract

Mucopolysaccharidosis III is a rare genetic disease characterized by progressive cognitive decline and severe hyperactivity that does not respond to stimulants. Somatic features are relatively mild. Patients are often initially misdiagnosed as having idiopathic developmental delay, attention deficit/hyperactivity disorder and/or autism spectrum disorders, putting them at risk for unnecessary testing and treatments.

Conclusion: Children with developmental or speech delay, especially those with a characteristic somatic feature or behavioural abnormalities, should be screened for MPS III.

Figure 1

Gallery of facial images from patients of various ages with MPS III. Not all affected patients have discernible facial dysmorphisms. Because of the variability in disease progression, early diagnosis does not always mean diagnosis in a young child; here we represent a variety of ages. The sex, MPS III subtype and age of the patients are as follows: (a) male, MPS IIIC, 10 years; (b) male, MPS IIIB, 21 years; (c) male, MPS IIIA, 43 years; (d) male, MPS IIIC, 10 years; (e) female, MPS IIIC, 13 years; (f) female, MPS IIIB, 18 years; (g) male, MPS IIIB, 11 years; (h) female, MPS IIIC, 4 years; (i) female, MPS IIIA, 20 years; (j) male, MPS IIIA, 10 years; (k) male, MPS IIIA, 6 years; (l) male, MPS IIIA, 11 years; (m) female, MPS IIIB, 20 years; (n) male, MPS IIIA, 12 years; (o) female, MPS IIIA, 14 years. MPS III, mucopolysaccharidosis type III.

Figure 2

Diagnostic algorithm for mucopolysaccharidosis (MPS) III. MPS III, mucopolysaccharidosis type III; uGAG, urinary glycosaminoglycan.