Ability change across multiple domains in mucopolysaccharidosis (Sanfilippo syndrome) type IIIA

The objective of this paper is 1) to expand the scope of the domains previously published in a natural history study of Mucopolysaccharidosis IIIA (Sanfilippo syndrome type A) (MPS IIIA) and 2) to present evidence regarding the capacity of a new metric, Growth Scale Values (GSVs), in comparison with traditional metrics, to show changes in skills as assessed by the Bayley Scales of Infant Development -III (BSID-III) and the Vineland Adaptive Behavior Scales, Second Edition (VABS-II). We re-analyzed a cohort of 25 children, 20 with rapid progressing disease and 5 with slow progression, who had been followed over two years using the BSID-III, and the VABS-II. Previously findings were reported using age equivalent scores; now we are also presenting findings with GSVs. For the re-analysis, Language and Motor scores were added to the Cognitive scale on the BSID-III, and Domain- and Subdomain-level scores added to the Total VABS-II score (i.e., ABC Composite). We evaluated raw scores, age equivalent scores, and GSVs (and standard scores for the VABS-II only). Individual patient data can be found in the appendices to this publication. Results indicate that 1) Cognition as measured by GSVs was the most sensitive to decline; 2) GSVs showed significant decline in the range of 4 to 6 years of age; 3) For children under 4 years of age, positive growth occurs on most scales and most metrics, with the exception of language which slows somewhat earlier; 4) Other than the Cognitive scale, Receptive Language on the BSID-III and Receptive Communication on the VABS-II showed the most sensitivity to change; 5) Gross Motor skills showed the least decline over time and appeared to lack sensitivity to MPS IIIA motor concerns; and 6) No evidence for sensitivity to change for any metric was found in time intervals less than one year. We conclude that GSVs are a precise measurement of change to detect decline in function, and they are a valuable method for future clinical trials in MPS IIIA. Evidence continues to support cognition as a primary endpoint. Additional work is needed to identify sensitive measures of meaningful endpoints to families.

Generalized pairwise comparisons of prioritized outcomes are a powerful and patient-centric analysis of multi-domain scores

BACKGROUND

Generalized pairwise comparisons (GPC) can be used to assess the net benefit of new treatments for rare diseases. We show the potential of GPC through simulations based on data from a natural history study in mucopolysaccharidosis type IIIA (MPS IIIA).

METHODS

Using data from a historical series of untreated children with MPS IIIA aged 2 to 9 years at the time of enrolment and followed for 2 years, we performed simulations to assess the operating characteristics of GPC to detect potential (simulated) treatment effects on a multi-domain symptom assessment. Two approaches were used for GPC: one in which the various domains were prioritized, the other with all domains weighted equally. The net benefit was used as a measure of treatment effect. We used increasing thresholds of clinical relevance to reflect the magnitude of the desired treatment effects, relative to the standard deviation of the measurements in each domain.

RESULTS

GPC were shown to have adequate statistical power (80% or more), even with small sample sizes, to detect treatment effects considered to be clinically worthwhile on a symptom assessment covering five domains (expressive language, daily living skills, and gross-motor, sleep and pain). The prioritized approach generally led to higher power as compared with the non-prioritized approach.

CONCLUSIONS

GPC of prioritized outcomes is a statistically powerful as well as a patient-centric approach for the analysis of multi-domain scores in MPS IIIA and could be applied to other heterogeneous rare diseases.

Increased pituitary volumes in patients with Sanfilippo syndrome (mucopolysaccharidosis type 3, MPS III)

PURPOSE

To evaluate apparent pituitary gland enlargement in patients with Sanfilippo syndrome observed at our institution.

METHODS

Twelve patients with Sanfilippo syndrome with brain MRI were studied. Anterior, posterior, and whole pituitary volumes were estimated using the prolate ellipsoid volume calculation method (π/6 × L × W × H). Convexity along the upper pituitary margin (Elster's grade) was also measured. These values were compared to two age- and sex-matched groups (normal controls and patients with Hurler syndrome) using one-way ANOVA followed by Tukey's post hoc analysis for multiple comparisons.

RESULTS

In the Sanfilippo cohort, the mean whole pituitary volume was 529.9 mm, the mean anterior pituitary volume was 333.4 mm, and the mean posterior pituitary volume was 59.1 mm with Elster's grade of 4.2. In the control cohort, the mean whole pituitary volume was 217.4 mm, the mean anterior pituitary volume was 154.8 mm, and the mean posterior pituitary volume was 28.4 mm with Elster's grade of 2.5. In the Hurler syndrome cohort, the mean whole pituitary volume was 310.0 mm, the mean anterior pituitary volume was 178.2 mm, and the mean posterior pituitary volume was 35.4 mm with Elster's grade of 3.5.

CONCLUSION

In our cohort of patients with Sanfilippo syndrome, whole, anterior, and posterior pituitary volumes and degree of convexity along the upper pituitary border were all significantly greater than controls. The cause of these morphological changes is unclear, as is clinical correlation of the findings.

Clinical, biochemical, and molecular characterization of mucopolysaccharidosis type III in 34 Egyptian patients

Mucopolysaccharidosis type III (MPS III) is a rare autosomal recessive lysosomal storage disorder characterized by progressive neurocognitive deterioration. There are four MPS III subtypes (A, B, C, and D) that are clinically indistinguishable with variable rates of progression. A retrospective analysis was carried out on 34 patients with MPS III types at Cairo University Children's Hospital. We described the clinical, biochemical, and molecular spectrum of MPS III patients. Of 34 patients, 22 patients had MPS IIIB, 7/34 had MPS IIIC, 4/34 had MPS IIIA, and only 1 had MPS IIID. All patients presented with developmental delay/intellectual disability, and speech delay. Ataxia was reported in a patient with MPS IIIC, and cerebellar atrophy in a patient with MPS IIIA. We reported 25 variants in the 4 MPS III genes, 11 of which were not previously reported. This is the first study to analyze the clinical and genetic spectrum of MPS III patients in Egypt. This study explores the genetic map of MPS III in the Egyptian population. It will pave the way for a national registry for rare diseases in Egypt, a country with a high rate of consanguineous marriage and consequently a high rate of autosomal recessive disorders.

Evaluation of bone health in patients with mucopolysaccharidosis

INTRODUCTION

This study aimed to evaluate the relationship between clinical findings, height and weight standard deviation scores, 25-hydroxyvitamin D₃ (25(OH)D₃) level, and dual-energy X-ray absorptiometry (DXA) results in patients diagnosed with mucopolysaccharidosis (MPS), where effective current treatments such as enzyme replacement therapy (ERT) can be accessed.

MATERIALS AND METHODS

25(OH)D₃ level was measured in 126 patients with MPS (17 with MPS I, 14 with MPS II, 18 with MPS III, 33 with MPS IVA, and 44 with MPS VI; 24-524 months). DXA was performed in 45 of these patients (8 with MPS I, 4 with MPS II, 4 with MPS III, 12 with MPS IVA, and 17 with MPS VI; 62-197 months; all patients were under 18 when DXA was performed) to assess bone mineral density (BMD) of the lumbar spine.

RESULTS

In total, 67.5% patients had a short stature, and 50% of them were underweight for their age. Of the patients, 13.5% were immobile, 28.6% had 25(OH)D₃ deficiency, and 30.2% had an insufficient level of 25(OH)D₃. BMD z score of 45 patients was - 2.5 ± 1.7. In 40% patients, it was <  - 2. However, after correction for height-for-age z score (HAZ), HAZ-adjusted BMD z score was - 0.1 ± 0.9. In 2.2% patients, it was <  - 2.

CONCLUSION

The low BMD z score prevalence reported with DXA was misleadingly higher in children with MPS and short stature. To prevent exposure to unnecessary antiresorptive treatments in these children, the effect of severe short stature and bone geometry on DXA measurements should be considered; further studies on bone health are warranted.

Characterization of a spontaneous cell line from primary mouse fibroblasts as a model to study Sanfilippo syndrome

To evaluate a new approach to Mucopolysaccharidosis type IIIA (MPS-IIIA), work was initiated on primary fibroblasts from a well-known mouse model in which sulfamidase deficiency correlates with the accumulation of heparan sulfate - the hallmark of this disease. Once the culture of fibroblasts was established, we observed continuous proliferation with a rapid growth rate, loss of contact inhibition and late passage stability, corresponding to a spontaneously immortalized cell line. The presence of the single point D31N mutation was verified and both rapid and abundant intracellular accumulation of low molecular weight HS was observed, confirming both genotype and phenotype. This cell line is a potential in vitro model system for future studies of MPS-IIIA prior to employing animal models.

Caprine Mucopolysaccharidosis IIID: Fetal and Neonatal Brain and Liver Glycosaminoglycan and Morphological Perturbations

Mucopolysaccharidosis IIID (MPS IIID) is a lysosomal storage disease associated with deficient activity of the enzyme N-acetylglucosamine 6-sulfatase (EC 3.1.6.14), a lysosomal hydrolase in the heparan sulfate glycosaminoglycan (HS-GAG) degradation pathway. In caprine MPS IIID, enzyme replacement therapy reversed early postnatal systemic but not primary or secondary central nervous system (CNS) substrate accumulations. The caprine MPS IIID large animal model system was used in this investigation to define the developmental profile of morphological and biochemical perturbations to estimate a time frame for therapeutic intervention. Light and electron microscopy were used to compare the CNS, liver, and kidney of normal +/+, MPS IIID carrier +/-, and MPS IIID-affected -/- goat kids (kids), at 60, 113-114, 128-129, and 135 d gestation (dg) of a 150-d gestational period, at birth, and at 59-64 d of postnatal (d-pn) age. In the CNS of -/- kids, morphological correlations of HS-GAG and glycolipid accumulations were evident in early differentiating neurons at 60 dg. CNS and systemic developmental, regional, and cellular differences in -/- kids at all time points included more prominent and earlier accumulation of lucent, putative HS-GAG substrates in lysosomes of meningeal and perivascular macrophages and hepatic sinusoidal cells than in CNS, hepatic, or renal parenchymal cells. The amounts and compositions of HS-GAG substrates in the brain and liver of +/+, +/-, and -/- kids were determined at 60, 65, 113-114, and 128-135 dg, at birth, and 53-78 d-pn. In the CNS of -/- kids, HS-GAG concentrations were variable and exceeded those of age-matched control tissue samples in the third but not the second trimester. In contrast, hepatic HS-GAG levels in -/- kids exceeded control values at all time points evaluated and paralleled the progressive morphological alterations. CNS and hepatic HS-GAG compositions in -/- kids were similar to each other and were more complex at all pre- and postnatal ages than those from control kids. Based on the time frame of development of CNS lesions and biochemical perturbations, prenatal therapeutic intervention in caprine MPS IIID is likely to be necessary to prevent or ameliorate substantive CNS and systemic lesions.

[Propofol and fentanyl in Sanfilippo disease. Surgical intervention with adenotonsillectomy]

An intravenous anesthesia with propofol and fentanyl was used for adenotonsillectomy in a child affected by mucopolysaccharidosis. This technique proved to be safe and convenient without peri- and postoperative complications.