The Neurobehavioral Phenotype in Mucopolysaccharidosis Type IIIB: an Exploratory Study

OBJECTIVES

Our goal was to describe the neurobehavioral phenotype in mucopolysaccharidosis Type IIIB (MPS IIIB). Parents report that behavioral abnormalities are a major problem in MPS III posing serious challenges to parenting and quality-of-life for both patient and parent. Our previous research on MPS IIIA identified autistic symptoms, and a Klüver-Bucy-type syndrome as indicated by reduced startle and loss of fear associated with amygdala atrophy. We hypothesized that MPS IIIB would manifest similar attributes when assessed with the same neurobehavioral protocol.

METHODS

Ten patients with MPS IIIB were compared with 9 MPS IIIA patients, all older than 6. 8 younger children with Hurler syndrome (1H) were chosen as a comparison group for the Risk Room procedure; MPS IH does not directly affect social/emotional function and these younger children were closer to the developmental level of the MPS IIIB group. To examine disease severity, cognitive ability was assessed. Four evaluations were used: the Risk Room procedure (to measure social-emotional characteristics, especially fear and startle responses), the Autism Diagnostic Observation Schedule (ADOS), the Sanfilippo Behavior Rating Scale (SBRS), and amygdala brain volumes calculated from manually-traced MRI images.

RESULTS

The two groups are equivalent in severity and show severe cognitive impairment. On the ADOS, the MPS IIIB patients exhibited the same autistic features as IIIA. The IIIB means differed from MPS IH means on most measures. However, the IIIB group did not approach the Risk Room stranger, like the MPS IH group who kept their distance, but unlike the IIIA group who showed no fear of the stranger. On the SBRS, the MPS IIIB patients were described as more inattentive and more fearful, especially of new people than the MPS IIIA. Onsets of some disease characteristics appeared more closely spaced and slightly earlier in MPS IIIB than IIIA.

CONCLUSIONS

On most behavioral measures, MPS IIIB patients did not differ substantially from MPS IIIA patients over age six, demonstrating autistic features and a Klüver Bucy-like syndrome including lack of fear and poor attention. Delay in onset of behavioral symptoms was associated with later diagnosis in two patients. Lack of fear, poor attention, and autistic-like symptomatology are as characteristic of MPS IIIB as they are of MPS IIIA. A possible difference is that the some behavioral abnormalities develop more quickly in MPS IIIB, If this is so, these patients may become at risk for harm and present a challenge for parenting even earlier than do those with MPS IIIA. .In future clinical trials of new treatments, especially with respect to quality of life and patient management, improvement of these behaviors will be an essential goal. Because very young patients were not studied, prospective natural history documentation of the early development of abnormal behaviors in MPS IIIB is needed.

Mucopolysaccharidosis (MPS) Physical Symptom Score: Development, Reliability, and Validity

OBJECTIVES

We quantified medical signs and symptoms to construct the Physical Symptom Score (PSS) for use in research to assess somatic disease burden in mucopolysaccharidoses (MPS) to track disease and monitor treatments. We examined scoring reliability, its concurrent validity with other measures, and relationship to age in MPS type I.

METHODS

Fifty-four patients with MPS I (36 with Hurler syndrome treated with hematopoietic cell transplant and 18 with attenuated MPS I treated with enzyme replacement therapy), ages 5 to 18 years, were seen longitudinally over 5 years. The summation of frequency and severity of signs of specific organ involvement, surgeries, and hydrocephalus drawn from medical histories comprise the PSS. We examined relationship to age and to daily living skills (DLS) from the Vineland Adaptive Behavior Scale and physical quality of life from the Child Health Questionnaire (CHQ) for each group.

RESULTS

The PSS was associated with age in both groups, indicating increase in disease burden over time. The PSS was significantly negatively associated with DLS (r = -0.48) and CHQ (r = -0.55) in the attenuated MPS I but not in the Hurler group.

CONCLUSIONS

The association of somatic disease burden with physical quality of life and ability to carry out daily living skills suggests that the PSS will be useful in the measurement of disease and treatment effects in the attenuated MPS I group. Earlier treatment with transplant and differing parental expectations are possible explanations for its lack of association with other outcomes necessitating an adaptation for Hurler syndrome in the future.

Changes in biomarkers of bone resorption over the first six months after pediatric hematopoietic cell transplantation

Bone loss has been observed within the first six months after HCT in both children and adults. While there is some evidence that bone formation may be reduced in children after HCT, it is currently unknown whether bone resorption is increased. The objective of this prospective study was to evaluate changes in markers of bone resorption over the first six months after pediatric HCT. Twenty-six participants (eight females) aged 10.9 ± 3.4 yr entered the study prior to HCT. Bone resorption was measured by urine DPD and PYD, and by plasma NTX and CTX. Seventeen participants who completed day +30 visit and either day +100 or +180 visits were included in the analysis. DPD increased between days +30 and +100 (mean change, 11.3 nmol/nmol creatinine; p = 0.012) and between days +30 and +180 (13.7 nmol/nmol creatinine; p = 0.036). PYD increased between days +30 and +100 (32 nmBCE/L; p = 0.019). CTX increased between baseline and day +100 (5.9 μg/L; p = 0.012). Changes in NTX levels were not statistically significant. This study shows that markers of bone resorption increase in children after HCT, suggesting that increased resorption may be a contributing factor to the pathophysiology of bone loss after pediatric HCT.

Racial and ethnic differences in incident myocardial infarction in end-stage renal disease patients: The USRDS

African Americans have a greater risk of cardiovascular disease (CVD) than Caucasians in early chronic kidney disease; however, limited data describe racial and ethnic differences in the risk of incident myocardial infarction (MI) among patients with end-stage renal disease (ESRD). We conducted a prospective, observational cohort study among 271 102 incident dialysis patients receiving renal replacement therapy enrolled in the United States Renal Data System (USRDS) for whom Medicare was the primary insurer between 1995 and 2000. The incidence and risk of any MI (non-fatal or fatal) estimated by Cox proportional hazards models was the primary outcome of interest. Of those with prevalent CVD at baseline (118 708), 14 849 had an incident non-fatal MI compared with 9926 events for those without prevalent CVD (152 394). Patients with prevalent CVD had higher crude rates of combined fatal and non-fatal MI (99.3/1000 person-years vs 42.9/1000 person-years) compared with those without prevalent CVD. Among those with prevalent CVD, African Americans (adjusted relative risk (aRR)=0.65, 95% confidence interval (CI):0.62-0.68), Asian Americans (aRR=0.74, 95% CI: 0.66-0.83), and Hispanics (aRR=0.72, 95% CI: 0.68-0.77) were 26-35% less likely to have an incident MI compared to Caucasians. Similarly, among those without prevalent CVD, racial/ethnic minorities were 26-42% less likely to have an incident MI compared to Caucasians. We conclude that in a national setting where comparable access to dialysis and associated medical care, exist, racial/ethnic minorities were found to have a lower risk of non-fatal and fatal MI than Caucasians.