More Data Is Needed in All 4 Subtypes of Sanfilippo Syndrome

The first systemic literature review published by the Orphanet Journal of Rare Diseases indicates that higher-quality epidemiological data is needed in all 4 subtypes of Sanfilippo syndrome in order to effectively target resources for disease research and management.

Sanfilippo syndrome (mucopolysaccharidosis [MPS] III subtypes A, B, C, and D) is a rare autosomal recessive inherited metabolic disorder that causes progressive neurocognitive degeneration. (MPS IIIA and B are more commonly diagnosed than types C and D.) This degeneration occurs due to the missing or lack of certain enzymes that are needed to break down long chains of sugar molecules. The disease can have devastating and lethal effects on children, most of whom never reach adulthood.¹

The purpose of this systemic literature review was to gather and assess previously published epidemiological data, including various frequency measures and geographical variation on Sanfilippo syndrome.

Among the data collected, the criteria for the primary data included published epidemiological data that included various frequency measures, such as the incidence rate, cumulative incidence, lifetime risk, point relevance, and birth prevalence, as well as geographical variation on Sanfilippo syndrome.

Criteria for the secondary data collected included selected clinical characteristics and natural history of the disease, which were available from papers included for review on the occurrence of Sanfilippo syndrome. For all parameters, publications were analyzed for all subtypes of MPS III and specifically for MPS IIIA.

The following databases were used: Medline, Embase, Cochrane Database of Systematic Reviews, Academic Search Complete, Cumulative Index to Nursing and Allied Health Literature, and the Centre for Reviews and Dissemination. Specific terms related to Sanfilippo syndrome epidemiology were combined with epidemiological terms for each database search. No language restrictions or publication date restrictions were applied to the searches. Web pages of rare disease organizations were also searched. The snowball method was used to identify further studies in the reference lists of the included studies.

The systematic literature review complied with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, which is a generally accepted guideline for reporting systematic literature reviews. The quality of the included papers was assessed by the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist, which is a guideline for reporting observational studies. Papers of good, medium, poor, and very poor quality were defined as those that fulfilled >&thinsp;80%, 66—80%, 50–65%, and&thinsp;<&thinsp;50% of criteria, respectively.¹

According to the results, 116 publications out of 2,794 were found eligible. Forty-six papers were included in the qualitative synthesis following the full-text review. In reference to the results of the systematic literature review, the lifetime risk at birth ranges from 0.17—2.35 per 100,000 live births for all 4 subtypes of MPS III together, and from 0.00–1.62 per 100,000 live births for the most frequent subtype, MPS IIIA.

In conclusion, the systematic literature review further proves that Sanfilippo syndrome is a rare disease that involves 4 subtypes of MPS III that are characterized by genetic enzyme deficiencies that cause progressive cognitive impairment, diminished behavioral capacity, and death.

However, the systematic literature review also had limitations. One such possible limitation is that the literature searches focused mainly on the disease frequency measures; this leaves a high chance for missed published data on the natural history of Sanfilippo syndrome. Another potential limitation of the analysis is that non-English articles and articles for which the full text could not be accessed from this analysis were excluded.

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References:

1. Epidemiology of Sanfilippo syndrome: results of a systematic literature review. Orpahnet Journal of Rare Diseases. 10, Apr. 2018.