Potocki-Lupski syndrome: a microduplication syndrome associated with oropharyngeal dysphagia and failure to thrive

OBJECTIVE

Failure to thrive (FTT) is a feature of children with Potocki-Lupski syndrome (PTLS) [duplication 17p11.2]. This study was designed to describe the growth characteristics of 24 subjects with PTLS from birth through age 5 years in conjunction with relevant physical features and swallow function studies.

STUDY DESIGN

We evaluated 24 individuals with PTLS who were ascertained by chromosome analysis and/or array comparative genome hybridization. Clinical assessments included review of medical records, physical examination, otolaryngological examination, and swallow function studies. Measures of height and weight were converted to Z-scores.

RESULTS

The mean weight-for-age and weight-for-length Z-scores at birth were lower (P < .01) than the reference standard and did not change with age. A history of poor feeding, hypotonia, and FTT were reported in 92%, 88%, and 71%, respectively. Individuals with hypotonia had lower weight-for-age and body mass index-for-age Z-scores (P = .01). Swallow function studies demonstrated at least one abnormality in all subjects.

CONCLUSIONS

FTT is common in children with PTLS. We hypothesize that oropharyngeal dysphagia and hypotonia likely contribute to FTT in patients with PTLS and recommend that once a diagnosis is established, the individual be assessed for feeding and growth issues and be availed of oromotor therapy and nutritional services.

Rett syndrome diagnostic criteria: lessons from the Natural History Study

Analysis of 819 participants enrolled in the Rett syndrome (RTT) Natural History Study validates recently revised diagnostic criteria. 765 females fulfilled 2002 consensus criteria for classic (653/85.4%) or variant (112/14.6%) RTT. All participants classified as classic RTT fulfilled each revised main criterion; supportive criteria were not uniformly present. All variant RTT participants met at least 3 of 6 main criteria in the 2002, 2 of 4 main criteria in the current format, and 5 of 11 supportive criteria in both. This analysis underscores the critical role of main criteria for classic RTT; variant RTT requires both main and supportive criteria.

Epilepsy and the natural history of Rett syndrome

BACKGROUND

Rett syndrome (RTT) is a neurodevelopmental disorder primarily seen in females, most with a mutation in MECP2. Epilepsy has been reported in 50%-80%. Previous reports were based on small sample sizes or parent-completed questionnaires, or failed to consider the impact of specific MECP2 mutations.

METHODS

The Rare Disease Consortium Research Network for RTT is an NIH-funded project to characterize the clinical spectrum and natural history of RTT in advance of clinical trials. Evaluations include clinical status (classic vs atypical RTT), MECP2 mutations, clinical severity, and presence, frequency, and treatment of seizures.

RESULTS

Enrollment as of June 2008 is 602; 528 (88%) meet clinical criteria for classic RTT. Of these, 493 (93%) have MECP2 mutations. Age range was 8 months to 64 years. A total of 360 (60%) were reported to have seizures, including 315 (60%) classic and 45 (61%) atypical RTT. Physician assessment of the 602 indicated that 48% had seizures. There was no significant difference in seizure occurrence by race/ethnicity. A significant age impact for seizures was seen and seizures were infrequent before age 2 years. MECP2 mutations most frequently associated with epilepsy were T158M (74%) and R106W (78%), and less frequently R255X and R306C (both 49%). Individuals with seizures had greater overall clinical severity, and greater impairment of ambulation, hand use, and communication.

DISCUSSION

Seizures are common in Rett syndrome, have an age-related onset and occurrence, vary by mutation, and are associated with greater clinical severity. This information represents a key consideration for designing clinical trials.

Profiling scoliosis in Rett syndrome

To understand scoliosis, related comorbidities, and phenotype-genotype correlations in individuals with Rett syndrome (RTT), the Rare Disease Clinical Research Network database for RTT was probed. Clinical evaluations included a detailed history and physical examination, comprehensive anthropometric measurements, and two quantitative measures of clinical status, Clinical Severity Scale (CSS) and motor-behavioral analysis (MBA). All data were exported to the Data Technology Coordinating Center (DTCC) at the University of South Florida. Scoliosis assessment was based on direct examination and curvature measurements by radiography (Cobb angle). Statistical analyses included univariate and multiple logistic regression models, adjusting for age at enrollment or mutation type. Scoliosis data were available from 554 classic RTT participants, mean age = 10 y (0-57 y). Scoliosis was noted in 292 (53%); mean age = 15 y with scoliosis and 6 y without. Using multiple regression analysis, MBA severity score, later acquisition, loss or absent walking, and constipation were associated with scoliosis. Two common methyl-CpG-binding protein 2 (MECP2) mutations, R294X and R306C, had reduced risk for scoliosis. These findings corroborated previous reports on scoliosis and extended understanding of comorbidities, clinical severity, and relative risk reduction for specific mutations. Clinical trial design should account for scoliosis and related factors judiciously.

A study of the treatment of Rett syndrome with folate and betaine

We tested the hypothesis that increasing methyl-group pools might promote transcriptional repression by other methyl-binding proteins or by mutant methyl-CpG-binding protein 2 with altered affinity, ameliorating the clinical features of Rett syndrome. A 12-month, double-blind, placebo-controlled folate-betaine trial enrolled 73 methylCpG-binding protein 2 mutation positive female participants meeting consensus criteria for Rett syndrome. Participants were randomized as young (< age 5 years) or old (>or= age 5 years). Structured clinical assessments occurred at baseline, 3, 6, and 12 months. Primary outcome measures included quantitative evaluation of breathing and hand movements during wakefulness, growth, anthropometry, motor/behavioral function, and qualitative evaluations from electroencephalograms and parent questionnaires. In all, 68 participants completed the study. Objective evidence of improvement was not found. Subjective improvement from parent questionnaires was noted for the <5 years group. This study should inform future treatment trials regarding balancing participants with specific mutations and comparable severity to minimize selection bias.

Bone mineral content and bone mineral density are lower in older than in younger females with Rett syndrome

Although bone mineral deficits have been identified in Rett syndrome (RTT), the prevalence of low bone mineral density (BMD) and its association with skeletal fractures and scoliosis has not been characterized fully in girls and women with RTT. Accordingly, we measured total body bone mineral content (BMC) and BMD using dual energy x-ray absorptiometry in a cross-sectional group of 50 females, aged 2-38 y, with RTT. Methyl-CpG-binding 2 (MECP2) mutations, skeletal fractures, and scoliosis were documented. The prevalence of BMC and BMD z scores < or-2 SD was 59 and 45%, respectively. Although absolute BMC and BMD increased significantly with increasing age, BMC, and BMD z scores were significantly lower in older than in younger females. The prevalence of fractures and scoliosis was 28 and 64%, respectively. Low BMD z scores were positively associated with fractures and scoliosis. Deficits in BMD were identified across a broad range of MECP2 mutations. This study identified associations among low BMD, fractures, and scoliosis, and underscored the need for better understanding of the molecular mechanisms of MECP2 in the regulation of bone mineral metabolism.

Nutrition support for neurologically impaired children: a clinical report of the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition

Undernutrition, growth failure, overweight, micronutrient deficiencies, and osteopenia are nutritional comorbidities that affect the neurologically impaired child. Monitoring neurologically impaired children for nutritional comorbidities is an integral part of their care. Early involvement by a multidisciplinary team of physicians, nurses, dieticians, occupational and speech therapists, psychologists, and social workers is essential to prevent the adverse outcomes associated with feeding difficulties and poor nutritional status. Careful evaluation and monitoring of severely disabled children for nutritional problems are warranted because of the increased risk of nutrition-related morbidity and mortality.

Fractional calcium absorption is increased in girls with Rett syndrome

BACKGROUND

Rett syndrome (RTT), an X-linked neurodevelopmental disorder primarilyaffecting girls, is characterized in part by osteopenia and increased risk of skeletal fractures. We hypothesized that decreased intestinal calcium (Ca) absorption relative to dietary Ca intake and increased renal Ca excretion might cause these problems in RTT.

OBJECTIVE

We measured fractional Ca absorption, urinary Ca loss, dietary Ca intake, and the hormonal factors regulating Ca metabolism to determine whether abnormalities in Ca balance might relate to poor bone mineralization in RTT girls and to evaluate the contribution of these factors to the overall dietary Ca needs of RTT girls.

STUDY DESIGN

Ten RTT girls and 10 controls, matched for age, sex, and pubertal status, were given a 3 day constant Ca diet that mimicked their habitual intakes. At the end of each dietary period, girls received single doses of Ca (intravenous) and Ca (oral). Fractional urinary excretion of Ca, Ca, 24 hour urinary Ca, and urinary cortisol excretion were determined. Serum Ca, phosphorous, alkaline phosphatase, vitamin D metabolites, parathyroid hormone (PTH), and osteocalcin were measured in the postabsorptive state. Bone mineral content (BMC) was measured by dual-energy x-ray absorptiometry.

RESULTS

Fractional Ca absorption was significantly higher in RTT than in control girls (mean +/- SDp, 52 vs. 33 +/- 13%). Dietary Ca intake (mean +/- SDp, 1,100 vs. 1,446 +/- 440 g/d) and net Ca absorption (mean +/- SDp, 513 vs. 362 +/- 306 mg/d) did not differ significantly between RTT and controls, respectively. Although urinary Ca excretion did not differ between groups, the increased urinary Ca:creatinine ratio (mean +/- SDp, 0.39 vs. 0.23 +/- 0.38) was consistent with clinical hypercalcuria and paralleled the significantly increased urinary cortisol excretion (mean +/- SDp, 3.1 vs. 1.7 +/- 1.1 mg/kg lean body mass per day) in the RTT girls. BMC was significantly lower in RTT than in controls (mean +/- SDp, 527 vs. 860 +/- 275 g). Serum Ca, P, alkaline phosphatase, vitamin D metabolites, PTH, and osteocalcin concentrations did not differ between the groups.

CONCLUSION

Fractional Ca absorption showed a compensatory increase in the presence of adequate dietary Ca intakes, mild hypercalcuria, and pronounced bone mineral deficits in RTT girls. Whether supplemental dietary Ca could enhance fractional Ca absorption and improve bone mineralization in RTT girls is unknown.

Ethical issues, safety, and data integrity in clinical trials

Published in 1974, the Belmont Report established the ethical principles for conducting clinical research in the United States. The essential concepts are respect for the research participant, beneficence for society at large, and justice (equal access to participation and equal treatment) toward subjects in a research study. These principles are applied through the use of informed consent, risk/benefit assessment, and the impartial selection of study subjects. Strict adherence to these criteria often results in conflicts of interest, which the investigator must anticipate and manage. Investigators must also be thoroughly acquainted with the principles of Good Clinical Practice and regulatory requirements. Recent implementation of the Privacy Rule now requires the investigator to protect not only the safety but the privacy of the research subject. While the regulatory obligations can appear onerous, strict compliance results in clinical research that is safe, scientifically sound, and ethical.

Growth characteristics of children with ectodermal dysplasia syndromes

OBJECTIVE

Clinical observations suggested that growth abnormalities may be present in children with ectodermal dysplasia (ED) syndromes. This study characterizes the longitudinal pattern of growth in a cohort of children with the ED syndromes. We hypothesized that (1) linear and ponderal growth abnormalities are present in children with ED from infancy through adolescence, and (2) linear and ponderal growth abnormalities differ among the clinical variants of these disorders.

METHODS

We studied 138 children who had ED and were registered with the National Foundation for Ectodermal Dysplasias, 74% of whom had clinical features consistent with the hypohidrotic EDs (HEDs). Height (or length) and weight measurements were obtained by standardized techniques and from review of available medical records. We converted these measurements to weight-for-height (children younger than 5 years and <103 cm in length) or BMI (children > or =2 years old). Height, weight, weight-for-height, and BMI were converted to age- and gender-specific z scores. We applied linear regression, 1-sample t tests, and analysis of variance to detect linear and ponderal growth abnormalities in children with ED compared with a reference population.

RESULTS

Mean weight-for-age, weight-for-height, and BMI-for-age z scores but not height-for-age z score, were significantly lower in children with the ED syndromes than in the reference population. Mean weight-for-age and weight-for-height z scores but not BMI-for-age or height-for-age z scores increased significantly with increasing age. The mean height-for-age z score of children with the ED syndromes other than the HEDs was significantly lower than that of children with the HEDs.

CONCLUSIONS

Growth abnormalities, measured as weight deficits, were present at an early age in children with the ED syndromes and persisted through adolescence. Height deficits were seen only in children with ED syndromes other than HEDs. Clinicians should evaluate carefully children with ED syndromes for growth abnormalities.

Nutrition support for pediatric patients with inflammatory bowel disease: a clinical report of the North American Society for Pediatric Gastroenterology, Hepatology And Nutrition

Impairment of growth and malnutrition are significant complications of inflammatory bowel disease (IBD) in pediatric patients. Since this topic was last reviewed in these pages (), a number of studies have further explored the epidemiology and pathogenesis of these nutritional complications of IBD in an effort to provide more effective interventions to prevent the long-term consequences of chronic nutrient deficiencies in childhood. In addition, during the past 15 years, the use of selected nutrients and microorganisms (probiotics) as primary or adjunctive therapy for the treatment of IBD has become an emerging area of great interest. The following is a Clinical Report from the Nutrition and Inflammatory Bowel Disease Committees of the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition.

Z score prediction model for assessment of bone mineral content in pediatric diseases

The objective of this study was to develop an anthropometry-based prediction model for the assessment of bone mineral content (BMC) in children. Dual-energy X-ray absorptiometry (DXA) was used to measure whole-body BMC in a heterogeneous cohort of 982 healthy children, aged 5-18 years, from three ethnic groups (407 European- American [EA], 285 black, and 290 Mexican-American [MA]). The best model was based on log transformations of BMC and height, adjusted for age, gender, and ethnicity. The mean +/- SD for the measured/predicted in ratio was 1.000 +/- 0.017 for the calibration population. The model was verified in a second independent group of 588 healthy children (measured/predicted In ratio = 1.000 +/- 0.018). For clinical use, the ratio values were converted to a standardized Z score scale. The whole-body BMC status of 106 children with various diseases (42 cystic fibrosis [CF], 29 juvenile dermatomyositis [JDM], 15 liver disease [LD], 6 Rett syndrome [RS], and 14 human immunodeficiency virus [HIV]) was evaluated. Thirty-nine patients had Z scores less than -1.5, which suggest low bone mineral mass. Furthermore, 22 of these patients had severe abnormalities as indicated by Z scores less than -2.5. These preliminary findings indicate that the prediction model should prove useful in determining potential bone mineral deficits in individual pediatric patients.

Infant feeding: a critical look at infant formulas

Commercially available infant formulas serve as the best alternative to human milk when breastfeeding is not possible. Infant formulas are designed specifically to mimic the composition of human milk or the functional aspects of human milk feeding. This review highlights the issues related to the composition of infant formulas. The most hotly debated issue currently is whether to add long-chain polyunsaturated fatty acids to infant formulas. Other controversial topics include the safety and efficacy of soy-based protein formulas, protein quantity and quality as they relate to the infant's nutritional needs and feeding tolerance, and the replacement of lactose with other carbohydrate sources for specialized infant formulas. Recent modifications in the fat blend of infant formulas have led to improved fat digestibility. However, the full spectrum of benefits associated with the addition of nucleotides awaits further study. Modifications to infant formulas are made when the preponderance of scientific evidence suggests that the compositional change will better meet the nutritional needs of the infant.

Influence of mutation type and X chromosome inactivation on Rett syndrome phenotypes

We screened 71 sporadic and 7 familial Rett syndrome (RTT) patients for MECP2 mutations by direct sequencing and determined the pattern of X chromosome inactivation (XCI) in 39 RTT patients. We identified 23 different disease-causing MECP2 mutations in 54 of 71 (76%) sporadic patients and in 2 of 7 (29%) familial cases. We compared electrophysiological findings, cerebrospinal fluid neurochemistry, and 13 clinical characteristics between patients carrying missense mutations and those carrying truncating mutations. Thirty-one of 34 patients (91%) with classic RTT had random XCI. Nonrandom XCI was associated with milder phenotypes, including a mitigated classic RTT caused by a rare early truncating mutation. Patients with truncating mutations have a higher incidence of awake respiratory dysfunction and lower levels of cerebrospinal fluid homovanillic acid. Scoliosis is more common in patients with missense mutations. These data indicate that different MECP2 mutations have similar phenotypic consequences, and random XCI plays an important role in producing the full phenotypic spectrum of classic RTT. The association of early truncating mutations with nonrandom XCI, along with the fact that chimeric mice lacking methyl-CpG-binding protein 2 (MeCP2) function die during embryogenesis, supports the notion that RTT is caused by partial loss of MeCP2 function.

Oropharyngeal dysfunction and gastroesophageal dysmotility are present in girls and women with Rett syndrome

BACKGROUND

Feeding impairment frequently complicates the course of children with neurologic disorders and places them at risk for malnutrition and growth failure. Although feeding abnormalities have been reported in female patients with Rett syndrome, the mechanisms that account for these findings have not been elucidated fully. This study was designed to characterize the clinical features of oropharyngeal and gastroesophageal dysfunction and their impact on the dietary intake and nutritional status of female subjects with Rett syndrome.

METHODS

The clinical features of oropharyngeal and gastroesophageal dysfunction in 13 female patients with Rett syndrome, (age range, 3.7 to 25.7 years) were characterized by an oral feeding assessment, swallowing function study, and upper gastrointestinal series. Growth, nutritional status, and body composition were determined by stadiometry and anthropometry. Dietary intakes were determined from 3-day food records.

RESULTS

Oropharyngeal dysfunction and gastroesophageal dysmotility were present in 100% and 69%, respectively, of the study patients with Rett syndrome. The scope and severity of these abnormalities were apparent only by videofluoroscopy. Abnormalities of oropharyngeal function included poor tongue mobility, reduced oropharyngeal clearance, and laryngeal penetration of liquids and solid food during swallowing. Esophageal dysmotility included absent primary or secondary waves, delayed emptying, atony, the presence of tertiary waves, spasm, and gastroesophageal reflux. Gastric dysmotility included diminished peristalsis or atony. Lower dietary energy intakes were associated with persistence of residue in the valleculae and pyriform sinuses and less body fat.

CONCLUSION

The prevalence of oropharyngeal dysfunction and gastroesophageal dysmotility warrants early diagnostic evaluation and intervention strategies to improve the nutritional status of girls and women with RS.

Organ growth in Rett syndrome: a postmortem examination analysis

Rett syndrome is a disorder of unknown etiology in females that manifests as severe mental and motor retardation during the first years of life. A postnatal pattern of altered growth is its earliest clinical expression. Head growth decelerates during the first year of age and is followed by a decline in somatic (height/weight) growth. The decreased occipitofrontal circumference (OFC) is reflected in decreased brain size, and measurements of the dendrites of cortical neurons suggest that a developmental and growth arrest have occurred. To further document growth in Rett syndrome, measurements of organ weights, as recorded in 39 postmortem examination studies were compared with normal organ weights for females of comparable age and height. These organ weights suggest that the pattern of growth failure in Rett syndrome, as compared with other forms of mental handicap, such as Down syndrome and Turner's syndrome, may be unique. In Rett syndrome the rate of brain growth, as derived from OFC, decelerates after birth. The increment in normal brain weight after 4 years of age, the age of the first postmortem examinations, is not observed in the Rett brain. The heart, kidneys, liver, and spleen grow at the normally defined rate until 8-12 years of age, when their growth rate decelerates, but their growth continues achieving organ weights that are appropriate for the height of the female. Adrenal weights are normal. These observations suggest that despite a generalized decreased growth in Rett syndrome the brain may be preferentially affected in this syndrome.

Sensitive measures of nutritional status in children in hospital and in the field

Protein-energy malnutrition and obesity are the most common nutritional disorders that complicate the clinical course of children with neoplastic diseases. Sensitive measures of nutritional status should be used to detect these problems in children with cancer. Height and weight measurements are the mainstay of the nutritional assessment of the child. These measurements can be converted to growth velocities or to height-for-age and weight-for-height Z-scores or percent of expected values to provide a measure of the degree of under- or over-nutrition in the child. Skinfold thickness and circumference measurements of the arms, legs and/or trunk may be useful to characterize the changes in peripheral fat depots and muscle mass, respectively. However, the assessments of body composition using these measurements are subject to methodological error because selected skinfold sites are excluded. Whole-body potassium, measured by 40K counting, and total body water, measured by deuterium or 18O dilution, serve as "gold standards" to determine the lean body mass and body fat status of the child, but these techniques may not be practical in all settings. The assessment of the nutritional status of the child serves as a guide to early nutritional intervention. Indicators for early nutritional intervention include: (1) height-for-age and weight-for-height or -age Z-scores more than 2 SD below the mean for age, (2) height-for-age measurements less than 95% of expected, (3) weight-for-height measurements less than 90% or greater than 120% of expected and (4) height velocities less than 5 cm/year after 2 years of age. Early nutritional intervention is essential to restore normal body composition, reverse linear growth arrest, promote tolerance to chemotherapeutic and radiation regimens and improve the quality of life in children with cancer.

Increased energy expenditure associated with repetitive involuntary movement does not contribute to growth failure in girls with Rett syndrome

OBJECTIVE

To determine whether increased total daily energy expenditure (TDEE) associated with repetitive, involuntary movements contributes to growth failure in girls with Rett syndrome (RS).

STUDY DESIGN

Fourteen girls with RS and 11 healthy girls were studied for 10 days to obtain measurements of height, weight, body circumference, and skin-fold thickness with stadiometric and anthropometric methods; whole-body potassium by potassium 40 counting; 72-hour dietary energy intakes by test weighing; 24-hour activity patterns using observational methods; and TDEE using the doubly-labeled water technique.

RESULTS

TDEE, when adjusted for differences in lean body mass, did not differ significantly between girls with RS and healthy girls. Although girls with RS spent more waking hours in physical activity than their healthy counterparts (85%+/-10% vs. 73%+/-11% awake time per day, p < 0.05), their repetitive movements were not sufficiently intense to increase TDEE. However, girls with RS had significantly less lean body mass, but not body fat, which contributed to their lower absolute TDEE in comparison with that of healthy girls (845+/-251 vs. 1453+/-534 kcal/day, p < 0.01). Dietary energy intake, when adjusted for differences in body weight, was not significantly different in girls with RS compared with healthy girls.

CONCLUSIONS

Increased TDEE as a result of repetitive, involuntary movements does not explain the alterations in growth and body composition of girls with RS.

Lean body mass of well-nourished women is preserved during lactation

To determine whether the lean body mass of well-nourished women was mobilized to support milk protein output during lactation, the body composition of 10 lactating and 10 nonlactating women was examined longitudinally at 6-wk intervals between 6 and 24 wk postpartum and at 52 wk postpartum, and that of 10 nulliparous women was examined at equivalent intervals, by using clinical anthropometry and whole-body potassium counting. Milk production was determined at 6-wk intervals during the period of exclusive breast-feeding (6-24 wk postpartum) by the test-weighing procedure. Milk composition was determined by chemical analysis. Dietary intakes were determined at 6-wk intervals between 6 and 24 wk postpartum from 3-d food records with use of a nutrient database. Lean body mass was maintained in women who exclusively breast-fed their infants during the first 6 mo postpartum while consuming dietary protein in amounts that exceeded those of their nonlactating counterparts by 55%. The high protein intakes were sustained throughout lactation despite a progressive reduction by 32% of milk protein output. Lean body mass was preserved throughout lactation in well-nourished women, suggesting that the metabolic needs of milk protein production were met solely by higher protein intakes of the lactating women.