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.

De Novo Loss-of-Function Mutations in USP9X Cause a Female-Specific Recognizable Syndrome with Developmental Delay and Congenital Malformations.

Mutations in more than a hundred genes have been reported to cause X-linked recessive intellectual disability (ID) mainly in males. In contrast, the number of identified X-linked genes in which de novo mutations specifically cause ID in females is limited. Here, we report 17 females with de novo loss-of-function mutations in USP9X, encoding a highly conserved deubiquitinating enzyme. The females in our study have a specific phenotype that includes ID/developmental delay (DD), characteristic facial features, short stature, and distinct congenital malformations comprising choanal atresia, anal abnormalities, post-axial polydactyly, heart defects, hypomastia, cleft palate/bifid uvula, progressive scoliosis, and structural brain abnormalities. Four females from our cohort were identified by targeted genetic testing because their phenotype was suggestive for USP9X mutations. In several females, pigment changes along Blaschko lines and body asymmetry were observed, which is probably related to differential (escape from) X-inactivation between tissues. Expression studies on both mRNA and protein level in affected-female-derived fibroblasts showed significant reduction of USP9X level, confirming the loss-of-function effect of the identified mutations. Given that some features of affected females are also reported in known ciliopathy syndromes, we examined the role of USP9X in the primary cilium and found that endogenous USP9X localizes along the length of the ciliary axoneme, indicating that its loss of function could indeed disrupt cilium-regulated processes. Absence of dysregulated ciliary parameters in affected female-derived fibroblasts, however, points toward spatiotemporal specificity of ciliary USP9X (dys-)function.

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.

UNLABELLED: 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.