Transforming paediatric practice by leveraging on genomic medicine

Genomic medicine entails the use of an individual’s genomic information in his or her clinical care to aid diagnosis and personalise management. As genetic conditions significantly contribute to neonatal and paediatric morbidity and mortality, paediatricians can incorporate genomic medicine in their clinical practice. Through this review, we aim to describe the basic concepts of genomic medicine, discuss the types of genetic and genomic testing available, present examples of how genomics is already being used in paediatrics and summarise the challenges of genomic medicine. The purpose of this review is to help paediatricians decide the suitable genetic or genomic test, understand the possible outcomes of testing and appreciate the requirements of appropriate counselling of patients.

PIK3CA-associated developmental disorders exhibit distinct classes of mutations with variable expression and tissue distribution

Mosaicism is increasingly recognized as a cause of developmental disorders with the advent of next-generation sequencing (NGS). Mosaic mutations of PIK3CA have been associated with the widest spectrum of phenotypes associated with overgrowth and vascular malformations. We performed targeted NGS using 2 independent deep-coverage methods that utilize molecular inversion probes and amplicon sequencing in a cohort of 241 samples from 181 individuals with brain and/or body overgrowth. We identified PIK3CA mutations in 60 individuals. Several other individuals (n = 12) were identified separately to have mutations in PIK3CA by clinical targeted-panel testing (n = 6), whole-exome sequencing (n = 5), or Sanger sequencing (n = 1). Based on the clinical and molecular features, this cohort segregated into three distinct groups: (a) severe focal overgrowth due to low-level but highly activating (hotspot) mutations, (b) predominantly brain overgrowth and less severe somatic overgrowth due to less-activating mutations, and (c) intermediate phenotypes (capillary malformations with overgrowth) with intermediately activating mutations. Sixteen of 29 PIK3CA mutations were novel. We also identified constitutional PIK3CA mutations in 10 patients. Our molecular data, combined with review of the literature, show that PIK3CA-related overgrowth disorders comprise a discontinuous spectrum of disorders that correlate with the severity and distribution of mutations.

The clinical and molecular spectrum of PIK3CA-related developmental disorders are correlated with types of mutations, tissue distributions, and levels of mosaicism with the clinical phenotype.

Left Ventricular Non-compaction: Is It Genetic?

Left ventricular non-compaction (LVNC) is reported to affect 0.14 % of the pediatric population. The etiology is heterogeneous and includes a wide number of genetic causes. As an illustration, we report two patients with LVNC who were diagnosed with a genetic syndrome. We then review the literature and suggest a diagnostic algorithm to evaluate individuals with LVNC. Case 1 is a 15-month-old girl who presented with hypotonia, global developmental delay, congenital heart defect (including LVNC) and facial dysmorphism. Case 2 is a 7-month-old girl with hypotonia, seizures, laryngomalacia and LVNC. We performed chromosomal microarray for both our patients and detected chromosome 1p36 microdeletion. We reviewed the literature for other genetic causes of LVNC and formulated a diagnostic algorithm, which includes assessment for syndromic disorders, inborn error of metabolism, copy number variants and non-syndromic monogenic disorder associated with LVNC. LVNC is a relatively newly recognized entity, with heterogeneity in underlying etiology. For a systematic approach of evaluating the underlying cause to improve clinical care of these patients, a diagnostic algorithm for genetic evaluation of patients with LVNC is proposed.

Loeys-Dietz syndrome in a Southeast Asian Hospital: a case series

Loeys-Dietz syndrome (LDS) is a heritable connective tissue disease in which the activity of the transforming growth factor (TGF) beta signalling pathway is disrupted. The clinical features of LDS represent a clinical continuum that includes LDS type 1, with cutaneous, vascular, skeletal and craniofacial findings, and LDS type 2, with cutaneous, vascular and skeletal findings. We describe five Asian patients with genetically confirmed LDS with mutations in either the TGFBR1 or TGFBR2 gene. Their clinical features were similar to those reported in Caucasian patients. Two patients have novel mutations in TGFBR2. Transcatheter occlusion of patent ductus arteriosus (PDA) was safe and successful in three patients. Treatment with Losartan for aortic root dilatation was well tolerated in our patients, but the outcome is mixed. Among the three patients with follow-up data, aortic root dilatation has improved in two patients but continues to progress in the third patient despite treatment.

CONCLUSION

We describe two novel mutations in TGFBR2 leading to LDS; PDA is common in our patients and can be safely occluded via transcatheter procedure.

Use of deferiprone for iron chelation in patients with transfusion-dependent thalassaemia

AIM

To conduct a retrospective case analysis of the clinical efficacy and adverse effects of deferiprone in our population.

METHODS

All patients with transfusion-dependent thalassaemia at KK Hospital who have been on deferiprone were included in the study. Outcomes measured include the change in ferritin levels and cardiac T2* values during deferiprone therapy, and incidence of side effects.

RESULTS

Thirty-three (47.1%) of the total cohort of 70 patients have been on deferiprone, out of which 26 were on combination therapy with desferrioxamine. Majority of the patients (76%) had stable cardiac iron load during deferiprone therapy, and four patients with moderate to severe cardiac iron load showed improvement. Ten patients (30.3%) had improvement in their ferritin levels. Three patients (9.1%) developed mild neutropenia at 3, 18 and 26 months, respectively, and two patients (6.1%) had agranulocytosis at 4 and 10 months, respectively. Their neutrophil counts improved spontaneously after cessation of deferiprone. Thrombocytopenia developed in 27.3% of the patients and was transient in majority (77.8%) of the patients. Five patients (15.2%) developed arthritis that improved after cessation of deferiprone therapy, and one patient had transient arthralgia that resolved spontaneously. Three patients (9.1%) had nausea and abdominal pain.

CONCLUSION

Deferiprone effectively reduced or stabilised cardiac iron load in our patients. Thrombocytopenia, arthropathy, neutropenia and agranulocytosis are the most important side effects. It is recommended that patients on deferiprone have their full blood counts monitored weekly for the first year of therapy and subsequently fortnightly as long as they are on deferiprone.

Loeys-Dietz syndrome: a Marfan-like syndrome associated with aggressive vasculopathy

Loeys-Dietz syndrome is a recently-characterised genetic disorder with an autosomal-dominant inheritance due to mutations in the transforming growth factor beta-receptor Type 1 or Type 2 genes. We present a Chinese female neonate with genetically-confirmed Loeys-Dietz syndrome, cleft palate, hypertelorism, and an early dilatation of the aortic root and ascending aorta. This syndrome is associated with an aggressive arteriopathy, with an increased risk of dissection and rupture. Early diagnosis, close monitoring and early surgery may prolong the life in affected individuals. Losartan is an emerging therapy that may help slow down the rate of arterial dilatation.

SMN1 deletions among singaporean patients with spinal muscular atrophy

INTRODUCTION

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder characterised by degeneration of spinal cord anterior horn cells, leading to muscular atrophy. It is the second most frequent autosomal recessive disease among Caucasian populations with a prevalence of between 1 in 6000 and 1 in 10,000 live births, and a carrier frequency of about 1 in 50. The International SMA Consortium classification defines several types of SMA depending on the age of onset and clinical severity. In the past, the diagnosis of SMA was confirmed by muscle biopsy and, sometimes, electromyography. In 1990, SMA was linked to the 5q13 region of chromosome 5. In 1995, it was found that >95% of patients with SMA have homozygous deletions of exons 7 and 8 of the survival motor neurone 1 (SMN1) gene, one of the candidate genes identified within 5q13. The purpose of our study was to determine the frequency of SMN1 deletions in patients with known SMA and the impact of this on the diagnosis of SMA.

MATERIALS AND METHODS

Molecular analysis was performed on stored DNA and case notes were reviewed retrospectively.

RESULTS

Twenty-two (91.7%) out of 24 patients with all types of SMA were homozygously deleted for exons 7 and/or 8 of SMN1. We also report our experience with prenatal diagnosis of SMA.

CONCLUSIONS

Molecular studies can replace conventional investigations for SMA and have made the option of prenatal diagnosis possible for couples at risk.

Intussusception: a three-year review

INTRODUCTION

Intussusception is the commonest cause of intestinal obstruction in infants and young children.

MATERIALS AND METHODS

This report reviews the clinical presentation, investigations and outcomes of patients with intussusception treated at the KK Women's and Children's Hospital between 1 May 1997 and 30 April 2000.

RESULTS

The study population comprised 160 consecutive patients treated for intussusception at our hospital over this 3-year period. The commonest symptom was vomiting; present in 135 patients (84.4%). A palpable abdominal mass was present in 90 patients (56.3%). The classical features of vomiting, abdominal pain, abdominal mass and rectal bleeding were present together in only 12 patients (7.5%). Abdominal ultrasonography was performed in 155 patients. One hundred and fifty-two patients (98.1%) had the classical target lesion on ultrasonography. Air enema reduction was attempted in all except 6 patients. In the majority of patients (130 or 84.4%), the intussusception was reduced successfully by air enema reduction. There was no association between the duration of symptoms before radiological reduction and the outcome of radiological reduction.

CONCLUSIONS

As the four classical features of intussusception were present together in only 7.5% of our patients, a high index of suspicion is necessary when any of the signs and symptoms are present in an infant or young child. Abdominal ultrasonography is the diagnostic investigation of choice. Air enema reduction was successful in 84.4% of patients and the duration of symptoms did not reduce the success rate. Thus, air enema reduction should be attempted in most patients unless they have absolute contraindications.