Diagnosis guide for clinicians

Sanfilippo syndrome (MPS III): when to suspect it and what to test

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Sanfilippo syndrome, or mucopolysaccharidosis type III, is an autosomal recessive lysosomal disease with 4 subtypes, each a different enzyme deficiency in heparan sulfate breakdown.Source Wijburg 2013 misdiagnosis review

It presents as speech or developmental delay after a period of normal development, then severe hyperactivity, sleep disturbance and cognitive decline, with mild somatic signs.

Source Wijburg 2013 misdiagnosis review

In a Dutch study of 46 patients, the median time from first specialist visit to diagnosis was 33 months, unchanged from 1988 to 2017.

Source Kuiper 2018 Dutch diagnostic delay study

33 monthsMedian time from first specialist visit to diagnosis in 46 Dutch patients, and 39 months from the first GP visitKuiper 2018 Dutch diagnostic delay study

9%Patients in that Dutch study diagnosed before age 3, the age its authors tie to the best timing for treatmentKuiper 2018 Dutch diagnostic delay study

21.8 monthsMean age at treatment of the 17 children in the main efficacy analysis on the Fayuvi label for type AFayuvi prescribing information

E76.22ICD-10-CM code, Sanfilippo mucopolysaccharidosesNLM ICD-10-CM lookup

Orphanet recordORPHA:581 ↗

Inheritance

Autosomal recessive

Age of onset

Childhood

Prevalence

Under 1 per 1,000,000 point prevalence, United States
1 to 9 per 1,000,000 prevalence at birth, United States
1 to 9 per 1,000,000 point prevalence, Europe

Also called

MPS3, MPSIII, Mucopolysaccharidosis type III, Sanfilippo disease, Sanfilippo syndrome

Live from Orphanet (INSERM) via Orphadata, licensed CC BY 4.0, data version 2026-06-23.

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Patterns to test Red flags Often mistaken for What to test Family screening ICD-10 codes Once confirmed For the patient

Patterns that should prompt a test for Sanfilippo syndrome (MPS III)

Each sign below is common on its own, which is why Sanfilippo syndrome (MPS III) is missed. Published studies describe these combinations as the picture to act on. Rows are ordered from the highest published figure to the lowest, within each kind of measure.

Where testing finds it

Share of each screened or biopsied group found to have Sanfilippo syndrome (MPS III), from the cited studies. A bar spans the lowest to the highest published figure.

1
Developmental, behavioral or other signs that led a pediatrician to suspect MPS+Raised urine heparan sulfate on tandem mass spectrometry
153 children under 19 with signs compatible with MPS, referred for urine testing from pediatric clinics at 6 Taiwan medical centers
MPS was confirmed in 13 of 153 (8.5%), including 5 (3.3%) with type B; the dye-based test missed 2 of those 5 (Lin 2019).Lin 2019 Taiwan at-risk screening
3.3%
2
An autism spectrum disorder diagnosis+Metabolic screening, with urine GAG in selected cases
300 Turkish children with autism spectrum disorders who completed physical and metabolic investigations at an Istanbul center
MPS III was diagnosed in 1 of 300 (0.3%), among 9 children found to have an inherited metabolic disorder (Kiykim 2016).Kiykim 2016 Turkish autism study
0.3%

How often diagnosed patients show it

Share of patients already diagnosed who had the finding, in the group named on each row. Groups differ by age and type, so read each row with its group.

1
Speech delay+Coarse facial features, often subtle+Hyperactivity
55 Spanish patients with MPS IIIA, IIIB or IIIC, symptoms recorded before diagnosis
Before diagnosis, 85% had speech delay, 78% coarse facial features and 65% hyperactivity, at about age 3 (Delgadillo 2013).Delgadillo 2013 Spanish series
65% to 85%
2
Retinal dystrophy in an adult+Hypertrophic cardiomyopathy+Normal or mildly impaired cognition
12 adults from 6 families with mild or non-neuronopathic MPS III (11 type A, 1 type B), median age at diagnosis 43 years
Retinal dystrophy was present in 9 of 12 (75%) and hypertrophic cardiomyopathy in 8 of 12 (67%) (Nijmeijer 2019).Nijmeijer 2019 adult case series
67% to 75%
3
Speech or language delay as the first symptom+Coarse facial features+Hepatomegaly
46 children with MPS IIIA evaluated in Pittsburgh from 2000 to 2013
Speech or language delay was the first symptom in 48%; 76% had coarse facial features and 67% hepatomegaly (Buhrman 2014).Buhrman 2014 Pittsburgh type A series
48% to 76%
4
Autistic-like social behaviors acquired at age 3 to 4+Few restricted or repetitive behaviors+Lack of cognitive growth
21 children with MPS IIIA, mean age 54 months, assessed with ADOS Module 1
ADOS criteria for autism spectrum disorder were met by 13 of 21 (62%), including all 11 older than 46 months (Rumsey 2014).Rumsey 2014 ADOS study
62%
5
Adenotonsillectomy or ear tubes+Behavioral problems+Developmental delay, recurrent diarrhea or disturbed sleep
46 Dutch patients with MPS III at their first visit to a medical specialist, at a median age of 28 months
ENT surgery prompted the referral in 63%; 76% already had behavioral problems, 50% diarrhea and 46% developmental delay (Kuiper 2018).Kuiper 2018 Dutch diagnostic delay study
46% to 76%

Also described, without a comparable figure

Hyperactivity that does not respond to stimulants + Developmental or speech delay + Severe sleep disturbance: No figure is published; Wijburg and colleagues call a lack of response to stimulants or behavior-based interventions a key diagnostic clue.Wijburg 2013 misdiagnosis review

These figures describe published study groups. They are not the chance that any one patient has Sanfilippo syndrome (MPS III), and bars whose ranges overlap are not in a settled order.

Red flags for Sanfilippo syndrome (MPS III)

What the cited sources describe, grouped by life stage and organ. Each line links to its source.

Speech and development, ages 1 to 4

Mild global developmental delay or speech delay between ages 1 and 4, usually after a period of normal development.Sanfilippo consensus guideline
GeneReviews lists language and motor delays at ages 1 to 3, and says language is often more delayed than motor development.GeneReviews
Speech delay came before diagnosis in 85% of a Spanish series of 55 patients, at about age 3.Delgadillo 2013 Spanish series
A developmental plateau: in a prospective study, children with rapidly progressing type A plateaued by 30 months and regressed after 40 to 50 months.Shapiro 2016 prospective type A study

Behavior and sleep, from about age 3

Severe hyperactivity, impulsivity with little regard for safety, anxious behavior and autistic-like behavior that worsen over time.Wijburg 2013 misdiagnosis review
Hyperactivity that responds poorly or not at all to stimulant medication or behavior-based interventions, which Wijburg and colleagues call a key diagnostic clue.Wijburg 2013 misdiagnosis review
Sleep disturbance, reported in more than 90% of children, with trouble falling asleep, frequent night waking and wandering or shouting at night.Wijburg 2013 misdiagnosis review
Autistic-like social behaviors acquired between ages 3 and 4, with restricted interests and repetitive behaviors largely absent, in 21 children with type A.Rumsey 2014 ADOS study
A systematic review of 16 studies found speech, language and communication difficulties consistent with autism, while repetitive and restricted behaviors were less widely reported.Wolfenden 2017 systematic review
Loss of skills already learned; GeneReviews says regression may start as early as age 3 to 4 in rapidly progressing disease.GeneReviews

Ears, airway and gut

Recurrent otitis, chronic nasal congestion, more than 1 set of ear tubes or an earlier than usual adenotonsillectomy.Sanfilippo consensus guideline
In the Dutch study, 65% of patients were first referred to an ENT specialist, and 61% then had an adenotonsillectomy or ear tubes.Kuiper 2018 Dutch diagnostic delay study
Hearing loss, which GeneReviews describes as common and conductive, sensorineural or mixed.GeneReviews
Recurrent diarrhea, which came before diagnosis in 50% of the Spanish series, and recurrent otitis in 46%.Delgadillo 2013 Spanish series
Umbilical or inguinal hernia, colic-like episodes and chronic loose stools or constipation.Sanfilippo consensus guideline

Appearance and abdomen

Mildly coarse facial features, prominent eyebrows, hirsutism and very coarse, stiff hair, all of which can be very subtle.Wijburg 2013 misdiagnosis review
Macrocephaly or frontal bossing, which the consensus guideline calls noteworthy when present alongside speech delay.Sanfilippo consensus guideline
Hepatomegaly in only about half of patients and splenomegaly in very few, according to Wijburg and colleagues.Wijburg 2013 misdiagnosis review
Among 46 children with type A seen in Pittsburgh, 76% had coarse facial features and 67% had hepatomegaly.Buhrman 2014 Pittsburgh type A series

Older children and adults

Slowly progressing disease: among 44 Dutch patients with type B, 79% had an attenuated course and most lived well into adulthood.Valstar 2010 Dutch type B study
Valstar and colleagues say type B must be considered in developmental delay even without decline, and that coexisting behavioral problems are a key feature.Valstar 2010 Dutch type B study
Early-onset dementia, vision loss with retinitis pigmentosa or adult-onset cardiomyopathy in adults, according to the consensus guideline.Sanfilippo consensus guideline
Among 12 adults with a mild or non-neuronopathic phenotype, 9 had retinal dystrophy and 8 had hypertrophic cardiomyopathy.Nijmeijer 2019 adult case series

Family history

An affected brother or sister; GeneReviews gives each sibling of an affected child a 25% chance of being affected.GeneReviews
Sibling pairs are common in published series, with 5 pairs among the 55 Spanish patients.Delgadillo 2013 Spanish series

Sanfilippo syndrome (MPS III) is often mistaken for

Diagnoses patients commonly carry first, and why the sources say they are confused.

First diagnosis	Why it is confused
Autism spectrum disorder	GeneReviews says many children with MPS III are suspected of having autism before the correct diagnosis, because language delay and behavior come first.GeneReviews
ADHD	GeneReviews says children whose most prominent first feature is hyperactivity may be misdiagnosed with ADHD as their primary diagnosis.GeneReviews
Idiopathic speech delay	Wijburg and colleagues note that an isolated speech delay with normal development in other areas is not uncommon early on.Wijburg 2013 misdiagnosis review
Idiopathic or global developmental delay	The consensus guideline says these labels are often given without sufficient medical workup to identify Sanfilippo syndrome as the underlying disorder.Sanfilippo consensus guideline
Recurrent ear infections and enlarged adenoids or tonsils alone	Upper airway and middle ear problems were the most frequent reason for the first GP visit in the Dutch study.Kuiper 2018 Dutch diagnostic delay study
Hearing loss as the whole explanation for speech delay	Hearing loss was among the most common first symptoms in a Pittsburgh type A series, in 20%, alongside speech delay in 48%.Buhrman 2014 Pittsburgh type A series
Smith-Magenis syndrome	GeneReviews lists shared speech delay, sleep disturbance, outbursts and hyperactivity, and separates it by intellectual disability without regression.GeneReviews
MPS I, MPS II or multiple sulfatase deficiency	GeneReviews separates these by dysostosis multiplex, corneal clouding, dermatan sulfate in urine or deficiency of several sulfatases.GeneReviews
Dementia or psychiatric illness in adults	Wijburg and colleagues cite adults with dementia or behavioral disturbance who were not diagnosed until their sixth to eighth decade.Wijburg 2013 misdiagnosis review

Codes patients often carry before this diagnosis

For spotting the pattern in a problem list or registry. Descriptions are checked daily against NLM's ICD-10-CM service; this is not coding advice.

Autistic disorder F84.0

GeneReviews says many children with MPS III are suspected of having autism before the correct diagnosis.GeneReviews

Attention-deficit hyperactivity disorder, hyperactive, combined or unspecified type F90.1, F90.2, F90.9

Children whose most prominent first feature is hyperactivity may be misdiagnosed with ADHD, according to GeneReviews.GeneReviews

Expressive, mixed or unspecified developmental disorder of speech and language F80.1, F80.2, F80.9

Speech delay came before diagnosis in 85% of a Spanish series of 55 patients.Delgadillo 2013 Spanish series

Delayed milestone, lack of expected development, or other disorder of psychological development R62.0, R62.50, F88

The consensus guideline says idiopathic developmental delay is often diagnosed without workup that would identify Sanfilippo syndrome.Sanfilippo consensus guideline

Insomnia or sleep disorder, unspecified G47.00, G47.9

Sleep disturbance is reported in more than 90% of children with MPS III.Wijburg 2013 misdiagnosis review

Otitis media, unspecified, or chronic serous otitis media H66.90, H65.20

Recurrent otitis came before diagnosis in 46% of the Spanish series.Delgadillo 2013 Spanish series

Unspecified hearing loss H91.90

Hearing loss was a first symptom in 20% of 46 children with type A in a Pittsburgh series.Buhrman 2014 Pittsburgh type A series

Umbilical or unilateral inguinal hernia without obstruction or gangrene K42.9, K40.90

Umbilical hernia came before diagnosis in 22% of the Spanish series and inguinal hernia in 7%.Delgadillo 2013 Spanish series

Hepatomegaly, not elsewhere classified R16.0

Hepatomegaly was found in 67% of the Pittsburgh type A series.Buhrman 2014 Pittsburgh type A series

Pigmentary retinal dystrophy H35.52

Among 12 adults with a mild or non-neuronopathic phenotype, 9 had retinal dystrophy.Nijmeijer 2019 adult case series

Testing for Sanfilippo syndrome (MPS III), step by step

The testing order the cited guidance describes, by who it applies to. It summarizes published guidance and is not a plan for any one patient.

Children with unexplained speech delay, developmental delay or behavior change

Quantitative urine glycosaminoglycans (GAG)
Bodamer and colleagues describe a quantitative urine GAG assay, such as dimethylmethylene blue, as the first step and call filter paper spot tests obsolete.Bodamer 2014 laboratory review
Read the urine result against age
The consensus guideline accepts a first morning or random sample and strongly recommends age-related reference ranges, because GAG levels fall with age.Sanfilippo consensus guideline
GAG electrophoresis or heparan sulfate by tandem mass spectrometry
The consensus guideline recommends electrophoresis as the qualitative assay and says tandem mass spectrometry of specific GAG species is more sensitive and specific.Sanfilippo consensus guideline

Normal urine GAG but a suggestive picture

A negative urine screen with ongoing suspicion
The consensus guideline recommends follow-up with enzyme analysis or genetic testing, because of the significant rate of false negatives.Sanfilippo consensus guideline

Raised heparan sulfate, or clinical suspicion

Enzyme panel for all 4 subtypes
GeneReviews recommends testing all 4 enzymes together in leukocytes or cultured fibroblasts. Deficiency of 1 enzyme with normal activity of the other 3 fits that subtype.GeneReviews
Enzyme analysis as a first test
The consensus guideline calls leukocyte or fibroblast enzyme analysis the gold standard. It says the assay can be first line, particularly when a suitable urine sample is hard to obtain.Sanfilippo consensus guideline

Deficient type A or type D enzyme

A second sulfatase
The consensus guideline says at least 1 other sulfatase should be assayed to rule out multiple sulfatase deficiency.Sanfilippo consensus guideline

Deficient enzyme on a dried blood spot

Confirm a dried blood spot result
The consensus guideline says a deficient dried blood spot result should be confirmed by enzyme assay in leukocytes or fibroblasts, or by molecular analysis.Sanfilippo consensus guideline

Anyone with suggestive clinical and laboratory findings

Gene testing: SGSH, NAGLU, HGSNAT and GNS
GeneReviews describes a multigene MPS panel that includes deletion/duplication analysis. It attributes about 60% of MPS III to SGSH and 30% to NAGLU.GeneReviews

Children with nonspecific delay, regression or behavior problems

Exome or genome sequencing
GeneReviews says people in whom MPS III has not been considered are more likely to be diagnosed by genomic testing, most commonly exome sequencing.GeneReviews

Children with developmental delay or intellectual disability

Sequencing early in a delay workup
The 2021 ACMG guideline strongly recommends that exome or genome sequencing be considered as a first-tier or second-tier test for these patients.ACMG 2021 exome and genome guideline

Diagnosis first made by gene testing

Confirm a molecular result biochemically
The consensus guideline says a confirmatory biochemical assay should be done to confirm the pathogenicity of the variants.Sanfilippo consensus guideline

Anyone with suggestive clinical features

Two markers to confirm
The consensus guideline requires at least 2 of these: GAG accumulation, decreased enzyme activity, or pathogenic or likely pathogenic variants on molecular testing.Sanfilippo consensus guideline

Confirmed MPS III

Name the subtype
Fayuvi is indicated only for type A, for neurologic manifestations in pediatric patients with preserved neurodevelopmental function, according to its label.Fayuvi prescribing information

Where testing goes wrong

GeneReviews says normal urine GAG results cannot rule out an MPS disorder, particularly MPS III, and that sensitivity falls when urine is dilute.GeneReviews
Wijburg and colleagues cite a study in which urine GAG levels in 33 of 58 patients with MPS III overlapped substantially with controls.Wijburg 2013 misdiagnosis review
In a Taiwan screening program, the dye-based urine test missed 2 of 5 children with type B, while tandem mass spectrometry missed none.Lin 2019 Taiwan at-risk screening
In a 2026 Chinese series, 2 of 20 patients had urine GAG within normal limits.Su 2026 Chinese series
Wijburg and colleagues describe collecting first-morning urine on 3 consecutive days as a useful practice, to avoid dilute samples.Wijburg 2013 misdiagnosis review
Heparin migrates with heparan sulfate on electrophoresis, so urine placed in a heparinized tube can read as a false positive.Wijburg 2013 misdiagnosis review
The consensus guideline says spot tests such as the Berry spot test should no longer be used, because of false positives and false negatives.Sanfilippo consensus guideline
In fluorometric assays for type C, GeneReviews warns that beta-hexosaminidase deficiency could give a false positive result.GeneReviews
Urine GAG and enzyme assays cannot identify carriers; Wijburg and colleagues say molecular testing is the only way to identify them.Wijburg 2013 misdiagnosis review
Residual enzyme activity alone does not reliably separate a severe from an attenuated course, according to Wijburg and colleagues.Wijburg 2013 misdiagnosis review
A lack of overt facial dysmorphism, or a normal liver and spleen, does not rule out the diagnosis.Wijburg 2013 misdiagnosis review
An autism label can hold up on formal testing; 13 of 21 children with type A met ADOS criteria, including all 11 over 46 months.Rumsey 2014 ADOS study
Among 300 Turkish children with autism who had metabolic screening, 1 was diagnosed with MPS III; urine GAG was screened only in selected cases.Kiykim 2016 Turkish autism study
Late diagnosis is not limited to Europe. In Brazil, 68 patients with type A were diagnosed at a mean of 7.3 years, almost 4 years after symptom onset.Montenegro 2025 MPS Brazil Network survey
The Ultragenyx-funded Revvity enzyme panel lists type B but not types A, C or D, as posted on November 11, 2026.Ultragenyx MPS Testing Program
The consensus guideline notes that Sanfilippo syndrome is generally not included in routine newborn screening programs.Sanfilippo consensus guideline
The FDA says treatment was limited to managing symptoms until it approved Fayuvi for type A on September 17, 2026; earlier reviews predate that change.FDA press release, September 17, 2026
Orphanet records MPS III as ORPHA:581 and maps it to WHO ICD-10 category E76.2 as an inclusion term without its own code.Orphanet cross-references

Where to test

NIH Genetic Testing Registry: Sanfilippo syndrome: The parent record for MPS III. Most tests are filed under the 4 subtype records, which is where laboratories list single-gene, panel and enzyme tests. NIH does not independently verify submissions or endorse any laboratory.NIH GTR
NIH Genetic Testing Registry: MPS IIIA (SGSH): Lists SGSH sequencing, mucopolysaccharidosis and lysosomal gene panels, leukocyte and blood spot MPS III enzyme panels and urine GAG studies submitted by laboratories.NIH GTR
NIH Genetic Testing Registry: MPS IIIB, IIIC and IIID: Type B (NAGLU) is concept C0086648, type C (HGSNAT) is C0086649 and type D (GNS) is C0086650. This link opens the type B record.NIH GTR
Ultragenyx MPS Testing Program (Revvity Omics) (drugmaker-sponsored): Ultragenyx-funded, no-charge dried blood spot enzyme panel for patients suspected of having an MPS disorder. The posted panel covers MPS I, II, IIIB, IVA, IVB, VI and VII, and does not list types IIIA, IIIC or IIID. Ultragenyx receives de-identified data from the program.Ultragenyx MPS Testing Program

Family screening and referral

Who else in the family

MPS III is autosomal recessive; each sibling has a 25% chance of being affected and a 50% chance of being an asymptomatic carrier.GeneReviews
The consensus guideline says molecular testing should be offered to all patients, because it enables cascade screening of undiagnosed siblings and extended family.Sanfilippo consensus guideline
GeneReviews says carrier testing for at-risk relatives requires the family's pathogenic variants to be identified first.GeneReviews
Rumsey and colleagues studied 21 children that included 5 sibling pairs, with siblings diagnosed because of the first child's diagnosis.Rumsey 2014 ADOS study
The Fayuvi label's main efficacy population was treated at a mean age of 21.8 months, with a range of 3.0 to 32.9 months.Fayuvi prescribing information
Once the family variants are known, GeneReviews says prenatal testing and preimplantation genetic testing are possible.GeneReviews

Who to refer to

Wijburg and colleagues say patients with a confirmed diagnosis, or a strong clinical suspicion, should be promptly referred to a metabolic disease specialist.Wijburg 2013 misdiagnosis review
The consensus guideline says the primary care provider should start screening or diagnostic tests alongside referral, to avoid delaying the diagnosis.Sanfilippo consensus guideline
In the Dutch study, a clinical geneticist made the diagnosis in 35% of patients, a general pediatrician in 28% and a metabolic pediatrician in 26%.Kuiper 2018 Dutch diagnostic delay study
At diagnosis, GeneReviews recommends consultation with a clinical geneticist or genetic counselor, and neurologic examination or referral to a pediatric neurologist.GeneReviews
Ultragenyx says Fayuvi is available through a network of Qualified Treatment Centers, with details to be posted on fayuvi.com.Ultragenyx press release
Before Fayuvi, the label calls for anti-AAV9 antibody testing and does not recommend treatment at total binding antibody titers of 1:100 or higher.Fayuvi prescribing information

Find a specialist by state

From the CMS NPI Registry, a public directory of US clinicians by registered specialty. A listing is not an endorsement and says nothing about experience with Sanfilippo syndrome (MPS III); patient organizations and academic centers can often name experienced clinicians.

ICD-10-CM codes for Sanfilippo syndrome (MPS III)

For orders, referrals and prior authorization. Each code is checked daily against NLM's ICD-10-CM service.

E76.22Sanfilippo mucopolysaccharidosesCurrent in NLM's ICD-10-CM listNLM ICD-10-CM lookup

Once the diagnosis is confirmed

Sanfilippo syndrome type A drugs for prescribersA prescribing guide: Fayuvi.Open trials: 9Screen a de-identified patient against every recruiting Sanfilippo syndrome (MPS III) study on ClinicalTrials.gov.Patient and family pageThe plain-language Sanfilippo syndrome (MPS III) page, with trials, treatments and help paying.

For the patient: why your doctor ordered this test

Plain language a patient can read or take home.

Your child's doctor ordered these tests to look for Sanfilippo syndrome, also called MPS III.

Sanfilippo syndrome is a rare inherited condition in which the body cannot break down a sugar chain called heparan sulfate.

Early signs can look like speech delay, autism or ADHD, often with many ear infections, loose stools or poor sleep.

These signs are common in childhood and usually have other causes, which is why a test is needed to tell.

The tests may include a urine test, a blood test that measures 4 enzymes and a gene test.

A normal urine test does not always rule the condition out, so the doctor may still order the blood or gene test.

If Sanfilippo syndrome is found, the tests also show which of 4 types it is, called A, B, C and D.

Brothers and sisters may be offered testing, because the condition runs in families.

Questions clinicians ask about Sanfilippo syndrome (MPS III) testing

Which combinations of findings should prompt testing for Sanfilippo syndrome (MPS III)?

In published screening and biopsy studies, the highest yields came from developmental, behavioral or other signs that led a pediatrician to suspect MPS plus raised urine heparan sulfate on tandem mass spectrometry (3.3% of 153 children under 19 with signs compatible with MPS, referred for urine testing from pediatric clinics at 6 Taiwan medical centers), and from an autism spectrum disorder diagnosis plus metabolic screening, with urine GAG in selected cases (0.3% of 300 Turkish children with autism spectrum disorders who completed physical and metabolic investigations at an Istanbul center). Among patients already diagnosed, the most common combination began with speech delay, seen in 65% to 85% of 55 Spanish patients with MPS IIIA, IIIB or IIIC, symptoms recorded before diagnosis. These figures describe study groups, not any one patient's chance of having Sanfilippo syndrome (MPS III).

How long does it take to diagnose Sanfilippo syndrome?

A median of 33 months passed between the first specialist visit and diagnosis in a Dutch study of 46 patients. That delay did not improve from 1988 to 2017. Median age at diagnosis was 62 months, and 9% were diagnosed before age 3. A Pittsburgh series of 46 children with type A reported a median age at diagnosis of 35 months and a median delay of 24 months.

Can a normal urine GAG test rule out Sanfilippo syndrome?

No; in a Taiwan screening program the dye-based urine test missed 2 of 5 children with type B. GeneReviews says normal urine GAG results cannot rule out an MPS disorder, particularly MPS III. The consensus guideline recommends enzyme analysis or genetic testing when suspicion remains after a negative urine screen.

How often do children with Sanfilippo syndrome meet criteria for autism?

In a study of 21 children with type A, 13 (62%) met ADOS criteria for autism spectrum disorder, including all 11 older than 46 months. Social and affective abnormalities were most frequent, and restricted interests and repetitive behaviors were largely absent. The authors say MPS IIIA should be in the differential diagnosis when a child acquires autistic-like behaviors.

Which enzyme and gene define each Sanfilippo subtype?

There are 4 subtypes, each with its own gene: SGSH for type A, NAGLU for B, HGSNAT for C and GNS for D. GeneReviews attributes about 60% of MPS III to SGSH, 30% to NAGLU, 4% to HGSNAT and 6% to GNS. It recommends testing all 4 enzymes together. The consensus guideline adds a second sulfatase when the type A or D enzyme is deficient, to rule out multiple sulfatase deficiency.

Why does early diagnosis of Sanfilippo syndrome type A matter now?

The FDA approved Fayuvi for type A on September 17, 2026. The 17 children in its main efficacy analysis were treated at a mean age of 21.8 months. The label limits use to pediatric patients with preserved neurodevelopmental function. In a prospective study, children with rapidly progressing type A plateaued in development by 30 months and regressed after 40 to 50 months.

What is the ICD-10 code for Sanfilippo syndrome?

Sanfilippo syndrome is coded E76.22, Sanfilippo mucopolysaccharidoses, which is current in NLM's ICD-10-CM lookup checked November 11, 2026. A search of that lookup for Sanfilippo returns only this code, with no separate codes by subtype. Orphanet maps MPS III to the WHO ICD-10 category E76.2 as an inclusion term.

Sources

Mucopolysaccharidosis Type III. GeneReviews, University of Washington, Seattle, via NCBI Bookshelf; chapter first posted September 19, 2019 (Wagner VF, Northrup H) and drafted from that text; PubMed lists a revision dated October 6, 2026 (Aries C, Koehn A, Lindschau M, Muschol N), 2019-09-19.
Sanfilippo syndrome: consensus guidelines for clinical care. Orphanet Journal of Rare Diseases 2022;17:391 (Muschol N, Giugliani R, Jones SA, Muenzer J et al, MPS III Guideline Development Group; funded in part by Global Genes, BioMarin, Cure Sanfilippo Foundation and Sanfilippo Children's Foundation), via PubMed Central, 2022-10-27.
Mucopolysaccharidosis type III (Sanfilippo syndrome) and misdiagnosis of idiopathic developmental delay, attention deficit/hyperactivity disorder or autism spectrum disorder. Acta Paediatrica 2013;102(5):462-470 (Wijburg FA, Węgrzyn G, Burton BK, Tylki-Szymańska A; editorial assistance funded by Shire, and all 4 authors report Shire ties), via PubMed Central, 2013-02-06.
Failure to shorten the diagnostic delay in two ultra-orphan diseases (mucopolysaccharidosis types I and III): potential causes and implications. Orphanet Journal of Rare Diseases 2018;13:2 (Kuiper GA, Meijer OLM, Langereis EJ, Wijburg FA; partly funded by a Sanofi Genzyme grant), via PubMed Central, 2018-01-08.
Natural history of Sanfilippo syndrome type A. Journal of Inherited Metabolic Disease 2014;37(3):431-437 (Buhrman D, Thakkar K, Poe M, Escolar ML), via PubMed abstract; funding and disclosures not seen, 2013-11-23.
Natural history of Sanfilippo syndrome in Spain. Orphanet Journal of Rare Diseases 2013;8:189 (Delgadillo V, O'Callaghan Mdel M, Gort L, Coll MJ et al; supported by MPS España, no competing interests declared), via PubMed Central, 2013-12-06.
Acquired autistic behaviors in children with mucopolysaccharidosis type IIIA. The Journal of Pediatrics 2014;164(5):1147-1151 (Rumsey RK, Rudser K, Delaney K, Potegal M et al; supported in part by Shire, and 3 authors consult for Shire), via PubMed Central, 2014-02-25.
Symptoms of Autism Spectrum Disorder (ASD) in Individuals with Mucopolysaccharide Disease Type III (Sanfilippo Syndrome): A Systematic Review. Journal of Autism and Developmental Disorders 2017;47(11):3620-3633 (Wolfenden C, Wittkowski A, Hare DJ; no funding, no conflicts declared), via PubMed Central, 2017-08-30.
A Prospective Natural History Study of Mucopolysaccharidosis Type IIIA. The Journal of Pediatrics 2016;170:278-287 (Shapiro EG, Nestrasil I, Delaney KA, Rudser K et al; supported by Shire, with Shire employees among the authors), via PubMed Central, 2016-01-16.
Mucopolysaccharidosis type IIIB may predominantly present with an attenuated clinical phenotype. Journal of Inherited Metabolic Disease 2010;33(6):759-767 (Valstar MJ, Bruggenwirth HT, Olmer R, Wevers RA et al; funded by 2 Dutch foundations, Stichting Weeshuis der Doopsgezinden and Stichting Metakids), via PubMed abstract and PubMed Central PMC2992652, 2010-09-18.
The attenuated end of the phenotypic spectrum in MPS III: from late-onset stable cognitive impairment to a non-neuronopathic phenotype. Orphanet Journal of Rare Diseases 2019;14:249 (Nijmeijer SCM, van den Born LI, Kievit AJA, Stepien KM et al; private foundation grants, no competing interests declared), via PubMed Central, 2019-11-12.
The laboratory diagnosis of mucopolysaccharidosis III (Sanfilippo syndrome): A changing landscape. Molecular Genetics and Metabolism 2014;113(1-2):34-41 (Bodamer OA, Giugliani R, Wood T), via PubMed abstract; funding and disclosures not seen, 2014-07-16.
An At-Risk Population Screening Program for Mucopolysaccharidoses by Measuring Urinary Glycosaminoglycans in Taiwan. Diagnostics (Basel) 2019;9(4):140 (Lin HY, Lee CL, Lo YT, Tu RY et al; Taiwan government and MacKay Memorial Hospital grants, no conflicts declared), via PubMed Central, 2019-10-05.
Inherited metabolic disorders in Turkish patients with autism spectrum disorders. Autism Research 2016;9(2):217-223 (Kiykim E, Zeybek CA, Zubarioglu T, Cansever S et al), via PubMed abstract; funding and disclosures not seen, 2015-06-07.
Clinical and genetic landscapes of mucopolysaccharidosis type III in 20 Chinese patients. Orphanet Journal of Rare Diseases 2026;21:386 (Su X, Zhang Y, Zhao X, Yin X et al; Chinese public research grants, no competing interests declared), via PubMed Central, 2026-07-31.
Survey of Patients With Sanfilippo Type a (MPS IIIA) Disease Diagnosed by the MPS Brazil Network. American Journal of Medical Genetics Part A 2025;197(6):e64026 (Montenegro YHA, Trapp FB, Dos Santos-Lopes SS, da Silva KBL et al), via PubMed abstract; funding and disclosures not seen, 2025-02-24.
Exome and genome sequencing for pediatric patients with congenital anomalies or intellectual disability: an evidence-based clinical guideline of the American College of Medical Genetics and Genomics (ACMG). Genetics in Medicine 2021;23(11):2029-2037 (Manickam K, McClain MR, Demmer LA, Biswas S et al; ACMG Board of Directors), via PubMed abstract, 2021-07-01.
FAYUVI (rebisufligene etisparvovec-hopf) suspension for intravenous infusion, prescribing information, revised 09/2026. Ultragenyx Pharmaceutical Inc., via U.S. Food and Drug Administration, 2026-09-17.
FDA Approves First Gene Therapy for Pediatric Patients with Sanfilippo Syndrome Type A. U.S. Food and Drug Administration, 2026-09-17.
Ultragenyx Announces Approval of FAYUVI™ Gene Therapy, the First-Ever FDA-Approved Treatment for Sanfilippo Syndrome Type A (MPS IIIA). Ultragenyx, 2026-09-17.
Ultragenyx MPS Testing Program. Revvity Omics (program funded by Ultragenyx; page revision 08/2025), 2026-11-11.
Mucopolysaccharidosis type 3, ORPHA:581, rare disease cross-referencing (Orphadata API). Orphanet, INSERM, via Orphadata, CC BY 4.0, 2026-06-23.
NIH Genetic Testing Registry tests for Sanfilippo syndrome, concept C0026706 (10 tests), and for MPS-III-A C0086647 (65), MPS-III-B C0086648 (62), MPS-III-C C0086649 (55) and MPS-III-D C0086650 (49), as listed in NCBI E-utilities on November 11, 2026. National Center for Biotechnology Information, NIH, 2026-11-11.
ICD-10-CM search results for "E76.22" (Clinical Table Search Service). National Library of Medicine, 2026-11-11.

A reference for licensed professionals, checked against its sources on November 11, 2026. It summarizes what the cited guidance says and does not tell anyone how to diagnose or treat a specific patient. Guidelines change; the current guideline and the treating clinician's judgment govern. Trial Friend is an independent information service, not a medical provider.