Prevalence and management of gastrointestinal manifestations in Silver-Russell syndrome

Imprinting disorders

Imprinting disorders (ImpDis) are congenital conditions that are characterized by disturbances of genomic imprinting. The most common individual ImpDis are Prader-Willi syndrome, Angelman syndrome and Beckwith-Wiedemann syndrome. Individual ImpDis have similar clinical features, such as growth disturbances and developmental delay, but the disorders are heterogeneous and the key clinical manifestations are often non-specific, rendering diagnosis difficult. Four types of genomic and imprinting defect (ImpDef) affecting differentially methylated regions (DMRs) can cause ImpDis. These defects affect the monoallelic and parent-of-origin-specific expression of imprinted genes. The regulation within DMRs as well as their functional consequences are mainly unknown, but functional cross-talk between imprinted genes and functional pathways has been identified, giving insight into the pathophysiology of ImpDefs. Treatment of ImpDis is symptomatic. Targeted therapies are lacking owing to the rarity of these disorders; however, personalized treatments are in development. Understanding the underlying mechanisms of ImpDis, and improving diagnosis and treatment of these disorders, requires a multidisciplinary approach with input from patient representatives.

Clinical and Molecular Heterogeneity of Silver-Russell Syndrome and Therapeutic Challenges: A Systematic Review

BACKGROUND

Silver-Russell syndrome (SRS) is a developmental disorder involving extreme growth failure, characteristic facial features and underlying genetic heterogeneity. As the clinical heterogeneity of SRS makes diagnosis a challenging task, the worldwide incidence of SRS could vary from 1:30,000 to 1:100,000. Although various chromosomal, genetic, and epigenetic mutations have been linked with SRS, the cause had only been identified in half of the cases.

MATERIAL AND METHODS

To have a better understanding of the SRS clinical presentation and mutation/ epimutation responsible for SRS, a systematic review of the literature was carried out using appropriate keywords in various scientific databases (PROSPERO protocol registration CRD42021273211). Clinical features of SRS have been compiled and presented corresponding to the specific genetic subtype. An attempt has been made to understand the recurrence risk and the role of model organisms in understanding the molecular mechanisms of SRS pathology, treatment, and management strategies of the affected patients through the analysis of selected literature.

RESULTS

156 articles were selected to understand the clinical and molecular heterogeneity of SRS. Information about detailed clinical features was available for 228 patients only, and it was observed that body asymmetry and relative macrocephaly were most prevalent in cases with methylation defects of the 11p15 region. In about 38% of cases, methylation defects in ICRs or genomic mutations at the 11p15 region have been implicated. Maternal uniparental disomy of chromosome 7 (mUPD7) accounts for about 7% of SRS cases, and rarely, uniparental disomy of other autosomes (11, 14, 16, and 20 chromosomes) has been documented. Mutation in half of the cases is yet to be identified. Studies involving mice as experimental animals have been helpful in understanding the underlying molecular mechanism. As the clinical presentation of the syndrome varies a lot, treatment needs to be individualized with multidisciplinary effort.

CONCLUSION

SRS is a clinically and genetically heterogeneous disorder, with most of the cases being implicated with a mutation in the 11p15 region and maternal disomy of chromosome 7. Recurrence risk varies according to the molecular subtype. Studies with mice as a model organism have been useful in understanding the underlying molecular mechanism leading to the characteristic clinical presentation of the syndrome. Management strategies often need to be individualized due to varied clinical presentations.

Epidemiology of Disorders Associated with Short Stature in Childhood: A 20-Year Birth Cohort Study in Finland

Background

Many primary and secondary disorders disturb growth and cause short stature (height below −2 SDS) in childhood. Growth monitoring programs aim at their early detection but are not evidence-based: epidemiology of childhood growth disorders is poorly characterized, and no consensus exists on priority target conditions. Herein, we describe population-based epidemiological data on several primary and secondary growth disorders associated with short stature in childhood.

Materials and Methods

This retrospective population-based 20-year birth cohort study examined 1 144 503 children (51% boys) born in Finland between 1998 and 2017, with 16.5 million care notifications including medical diagnoses. The first occurrences of key primary or secondary growth disorders were identified in multiple registers. Median ages at diagnosis (MAD), and age- and sex-specific cumulative incidences (CMI) from birth until 16 years of age were determined.

Results

Turner syndrome was the most common primary growth disorder (CMI 52 per 100 000 at 16 years, MAD 4.0 years). Most primary growth disorders were diagnosed before the age of 4 years, and thereafter, secondary growth disorders increased in number. MAD of growth hormone deficiency (GHD) was 8.7 (boys) and 7.2 years (girls). At 16 years, the CMI of GHD was higher in boys than in girls (127 versus 93 per 100 000, respectively), whereas the CMI of hypothyroidism was higher in girls (569 versus 306 per 100 000). Celiac disease was the most common secondary growth disorder and more common in girls than in boys (988 versus 546 per 100 000 at 16 years, respectively).

Conclusion

These population-based epidemiological data indicate that childhood growth monitoring should be age- and sex-specific. In the early childhood, the focus should be on primary growth disorders, and from preschool age also on secondary growth disorders. These results provide evidence for improving growth monitoring programs and diagnostic practices targeting on Turner syndrome, GHD, hypothyroidism, and celiac disease.

Height and body mass index in molecularly confirmed Silver-Russell syndrome and the long-term effects of growth hormone treatment

OBJECTIVE

Silver-Russell syndrome (SRS) causes short stature. Growth hormone (GH) treatment aims to increase adult height. However, data are limited on the long-term outcomes of GH in patients with molecularly confirmed SRS. This study evaluated height, body mass index (BMI) and GH treatment in molecularly confirmed SRS.

DESIGN

An observational study with retrospective data collection.

PATIENTS

Individuals with molecularly confirmed SRS aged ≥13 years.

MEASUREMENTS

Data were collected on height, height gain (change in height standard deviation score [SDS] from childhood to final or near-final height), BMI and gain in BMI (from childhood to adulthood) and previous GH treatment.

RESULTS

Seventy-one individuals (40 female) were included. The median age was 22.0 years (range 13.2-69.7). The molecular diagnoses: H19/IGF2:IG-DMR LOM in 80.3% (57/71); upd(7)mat in 16.9% (12/71) and IGF2 mutation in 2.8% (2/71). GH treatment occurred in 77.5% (55/71). Total height gain was greater in GH-treated individuals (median 1.53 SDS vs. 0.53 SDS, p = .007), who were shorter at treatment initiation (-3.46 SDS vs. -2.91 SDS, p = .04) but reached comparable heights to GH-untreated individuals (-2.22 SDS vs. -2.74 SDS, p = .7). In GH-treated individuals, BMI SDS was lower at the most recent assessment (median -1.10 vs. 1.66, p = .002) with lower BMI gain (2.01 vs. 3.58, p = .006) despite similar early BMI SDS to GH-untreated individuals (median -2.65 vs. -2.78, p = .3).

CONCLUSIONS

These results support the use of GH in SRS for increasing height SDS. GH treatment was associated with lower adult BMI which may reflect improved metabolic health even following discontinuation of therapy.

What Every Internist-Endocrinologist Should Know about Rare Genetic Syndromes in Order to Prevent Needless Diagnostics, Missed Diagnoses and Medical Complications: Five Years of 'Internal Medicine for Rare Genetic Syndromes'

Patients with complex rare genetic syndromes (CRGS) have combined medical problems affecting multiple organ systems. Pediatric multidisciplinary (MD) care has improved life expectancy, however, transfer to internal medicine is hindered by the lack of adequate MD care for adults. We have launched an MD outpatient clinic providing syndrome-specific care for adults with CRGS, which, to our knowledge, is the first one worldwide in the field of internal medicine. Between 2015 and 2020, we have treated 720 adults with over 60 syndromes. Eighty-nine percent of the syndromes were associated with endocrine problems. We describe case series of missed diagnoses and patients who had undergone extensive diagnostic testing for symptoms that could actually be explained by their syndrome. Based on our experiences and review of the literature, we provide an algorithm for the clinical approach of health problems in CRGS adults. We conclude that missed diagnoses and needless invasive tests seem common in CRGS adults. Due to the increased life expectancy, an increasing number of patients with CRGS will transfer to adult endocrinology. Internist-endocrinologists (in training) should be aware of their special needs and medical pitfalls of CRGS will help prevent the burden of unnecessary diagnostics and under- and overtreatment.

Chronic Hypercapnic Respiratory Failure in an Adult Patient with Silver-Russell Syndrome

A 31-year-old woman who was clinically diagnosed with Silver-Russell syndrome (SRS) in childhood was admitted with complaints of dyspnea. She had hypercapnic respiratory failure accompanied by nocturnal hypoventilation. Computed tomography revealed systemic muscle atrophy and superior mesenteric artery syndrome; however, the bilateral lung fields were normal. She was treated with nocturnal noninvasive positive pressure ventilation and showed improvement of respiratory failure. In this case, loss of methylation on chromosome 11p15 and maternal uniparental disomy of chromosome 7, which are the common causes of SRS, were not detected. This is a rare case of adult SRS manifesting as chronic hypercapnic respiratory failure.

Phenotype of genetically confirmed Silver-Russell syndrome beyond childhood

BACKGROUND

Silver-Russell syndrome is an imprinting disorder that restricts growth, resulting in short adult stature that may be ameliorated by treatment. Approximately 50% of patients have loss of methylation of the imprinting control region (H19/IGF2:IG-DMR) on 11p15.5 and 5%-10% have maternal uniparental disomy of chromosome 7. Most published research focuses on the childhood phenotype. Our aim was to describe the phenotypic characteristics of older patients with SRS.

METHODS

A retrospective cohort of 33 individuals with a confirmed molecular diagnosis of SRS aged 13 years or above were carefully phenotyped.

RESULTS

The median age of the cohort was 29.6 years; 60.6% had a height SD score (SDS) ≤-2 SDS despite 70% having received growth hormone treatment. Relative macrocephaly, feeding difficulties and a facial appearance typical of children with SRS were no longer discriminatory diagnostic features. In those aged ≥18 years, impaired glucose tolerance in 25%, hypertension in 33% and hypercholesterolaemia in 52% were noted. While 9/33 accessed special education support, university degrees were completed in 40.0% (>21 years). There was no significant correlation between quality of life and height SDS. 9/25 were parents and none of the 17 offsprings had SRS.

CONCLUSION

Historical treatment regimens for SRS were not sufficient for normal adult growth and further research to optimise treatment is justified. Clinical childhood diagnostic scoring systems are not applicable to patients presenting in adulthood and SRS diagnosis requires molecular confirmation. Metabolic ill-health warrants further investigation but SRS is compatible with a normal quality of life including normal fertility in many cases.

Sleep disordered breathing in Silver-Russell syndrome patients: a new outcome

OBJECTIVE

Imprinting disorders (ID), such as Prader-Willi syndrome (PWS), are associated with sleep-disordered breathing (SDB). No data are available for Silver-Russell syndrome (SRS), another ID that shares clinical features with PWS, although many patients describe excessive daytime sleepiness, disturbed sleep, and snoring. The aim of this study was to characterize sleep in children with SRS and to evaluate the impact of recombinant growth hormone (rGH) therapy.

METHODS

We performed a retrospective analysis of sleep recordings in 40 patients with molecularly proven SRS (methylation anomaly in 11p15 [n = 32] or maternal uniparental disomy of chromosome 7 [n = 16]). Sleep recordings were either by means of polygraphy or polysomnography (PSG) (n = 16). A total of 34 patients received rGH therapy.

RESULTS

We collected 61 sleep recordings. The mean apnea-hypopnea index (AHI) was 3.4 events/h (0-12.4), with a mean central AHI of 0.5 events/h (0-2.4). SDB was identified in 73.8% (n = 45) of the recordings and was severe in 4.9%. SDB was present in 86.4% of patients before rGH therapy and was severe in 13.6%. AHI worsened for 5 of 12 patients with sleep recordings before and after rGH therapy initiation, reaching mild impairment. The mean rGH dose was 32.3 μg/kg/(12.9-51.4), with a mean insulin-like growth factor 1 plasma level of 1.7 SDS (-1.9 to 6.6).

CONCLUSION

Most patients with SRS present with SDB with an obstructive profile, possibly explained by narrowing of the airways and lymphoid organ hypertrophy. We recommend systematic ear-nose-throat evaluation of SRS patients and PSG if there are clinical anomalies, preferably before initiating rGH therapy, to monitor and adapt the management of patients with SDB.

Children Born Small for Gestational Age: Differential Diagnosis, Molecular Genetic Evaluation, and Implications

Children born small for gestational age (SGA), defined as a birth weight and/or length below -2 SD score (SDS), comprise a heterogeneous group. The causes of SGA are multifactorial and include maternal lifestyle and obstetric factors, placental dysfunction, and numerous fetal (epi)genetic abnormalities. Short-term consequences of SGA include increased risks of hypothermia, polycythemia, and hypoglycemia. Although most SGA infants show catch-up growth by 2 years of age, ∼10% remain short. Short children born SGA are amenable to GH treatment, which increases their adult height by on average 1.25 SD. Add-on treatment with a gonadotropin-releasing hormone agonist may be considered in early pubertal children with an expected adult height below -2.5 SDS. A small birth size increases the risk of later neurodevelopmental problems and cardiometabolic diseases. GH treatment does not pose an additional risk.

Effect of Cyproheptadine on Weight and Growth Velocity in Children With Silver-Russell Syndrome

OBJECTIVES

Nutritional management of children with Silver-Russell syndrome (SRS) is crucial, especially before initiating growth hormone therapy. Since cyproheptadine (CYP) has been reported to be orexigenic, we retrospectively investigated the effects of CYP on changes in weight and height in patients with SRS.

METHODS

Anthropometric parameters (weight [W], length or height [H], weight on expected weight for height [W/H], and body mass index) were recorded for 34 children with SRS receiving CYP. We specifically analyzed the anthropometric parameters (expressed in median) in a group of 23 patients treated with CYP at baseline (M0-CYP) and every 3 months (M3 to M12-CYP) after the initiation of CYP treatment.

RESULTS

The 23 children with SRS treated by CYP only had weight stagnation during the months preceding the start of treatment. Anthropometric parameters, especially the weight, differed significantly between M0-CYP and all other times (M3, M6, M9, M12-CYP). After 1 year of treatment, a gain in overall length/height and weight was observed (W: +1.1 standard deviations from the mean [SDS]; H: +0.5 SDS). At M3, significant improvements in W/H (74.9% vs 79.3% [P = 0.01]) and body mass index (-3.4 vs -2.4 SDS [P = 0.001]) were also observed. Twenty-one patients (91%) improved their weight by at least +0.5 SDS, and 12 (52%) by at least +1 SDS.

CONCLUSIONS

Our results show that CYP can be effective in patients with SRS with significant improvements in growth velocity and nutritional status before initiation of growth hormone therapy. Further prospective studies are required to confirm these results.

Behavioural abnormalities in a novel mouse model for Silver Russell Syndrome

Silver Russell Syndrome (SRS) syndrome is an imprinting disorder involving low birth weight with complex genetics and diagnostics. Some rare SRS patients carry maternally inherited microduplications spanning the imprinted genes CDKN1C, PHLDA2, SLC22A18 and KCNQ1, suggesting that overexpression of one of more of these genes contributes to the SRS phenotype. While this molecular alteration is very rare, feeding difficulties are a very common feature of this condition. Given that SRS children also have very low body mass index, understanding the underpinning biology of the eating disorder is important, as well as potential co-occurring behavioural alterations. Here, we report that a mouse model of this microduplication exhibits a number of behavioural deficits. The mice had a blunted perception of the palatability of a given foodstuff. This perception may underpin the fussiness with food. We additionally report hypoactivity, unrelated to anxiety or motoric function, and a deficit in the appropriate integration of incoming sensory information. Importantly, using a second genetic model, we were able to attribute all altered behaviours to elevated expression of a single gene, Cdkn1c. This is the first report linking elevated Cdkn1c to altered behaviour in mice. Importantly, the findings from our study may have relevance for SRS and highlight a potentially underreported aspect of this disorder.

Diagnosis and management of Silver-Russell syndrome: first international consensus statement

This Consensus Statement summarizes recommendations for clinical diagnosis, investigation and management of patients with Silver-Russell syndrome (SRS), an imprinting disorder that causes prenatal and postnatal growth retardation. Considerable overlap exists between the care of individuals born small for gestational age and those with SRS. However, many specific management issues exist and evidence from controlled trials remains limited. SRS is primarily a clinical diagnosis; however, molecular testing enables confirmation of the clinical diagnosis and defines the subtype. A 'normal' result from a molecular test does not exclude the diagnosis of SRS. The management of children with SRS requires an experienced, multidisciplinary approach. Specific issues include growth failure, severe feeding difficulties, gastrointestinal problems, hypoglycaemia, body asymmetry, scoliosis, motor and speech delay and psychosocial challenges. An early emphasis on adequate nutritional status is important, with awareness that rapid postnatal weight gain might lead to subsequent increased risk of metabolic disorders. The benefits of treating patients with SRS with growth hormone include improved body composition, motor development and appetite, reduced risk of hypoglycaemia and increased height. Clinicians should be aware of possible premature adrenarche, fairly early and rapid central puberty and insulin resistance. Treatment with gonadotropin-releasing hormone analogues can delay progression of central puberty and preserve adult height potential. Long-term follow up is essential to determine the natural history and optimal management in adulthood.

New clinical and molecular insights into Silver-Russell syndrome

PURPOSE OF REVIEW

The purpose of review is to summarize new outcomes for the clinical characterization, molecular strategies, and therapeutic management of Silver-Russell syndrome (SRS).

RECENT FINDINGS

Various teams have described the clinical characteristics of SRS patients by genotype. A clinical score for the definition of SRS and for orienting molecular investigations has emerged. Insulin-like growth factor 2 (a major fetal growth factor) has been implicated in the pathophysiology of SRS, as the principle molecular mechanism underlying the disease is loss of methylation of the 11p15 region, including the imprinted insulin-like growth factor 2 gene. Maternal uniparental disomy of chromosome 7 and recently identified rare molecular defects have also been reported in patients with SRS. However, 40% of patients still have no molecular diagnosis.

SUMMARY

The definition of SRS has remained clinical since the first description of this condition, despite the identification of various molecular causes. The clinical issues faced by these patients are similar to those faced by other patients born small for gestational age (SGA), but patients with SRS require specific multidisciplinary management of their nutrition, growth, and metabolism, as they usually present an extreme form of SGA. Molecular analyses can confirm SRS, and are of particular importance for genetic counseling and prenatal testing.

New developments in Silver-Russell syndrome and implications for clinical practice

Silver-Russell syndrome is a clinically and genetically heterogeneous disorder, characterized by prenatal and postnatal growth restriction, relative macrocephaly, body asymmetry and characteristic facial features. It is one of the imprinting disorders, which results as a consequence of aberrant imprinted gene expressions. Currently, maternal uniparental disomy of chromosome 7 accounts for approximately 10% of Silver-Russell syndrome cases, while ~50% of patients have hypomethylation at imprinting control region 1 at chromosome 11p15.5 locus, leaving ~40% of cases with unknown etiologies. This review aims to provide a comprehensive list of molecular defects in Silver-Russell syndrome reported to date and to highlight the importance of multiple-loci/tissue testing and trio (both parents and proband) screening. The epigenetic and phenotypic overlaps with other imprinting disorders will also be discussed.