Epidemiological, clinical, pathological and genetic characteristics of epidermolysis bullosa in New Zealand.

OBJECTIVE: To establish the epidemiological, clinical, pathological and genetic characteristics of epidermolysis bullosa (EB) in New Zealand (NZ). METHODS: Participants were recruited through the Dystrophic Epidermolysis Bullosa Research Association of New Zealand (DEBRA NZ). Dedicated EB nurse medical records, Genetic Health Service NZ (GHSNZ) records and, where available, public hospital records were manually reviewed for relevant clinical data. RESULTS: Ninety-two participants took part in the study (56% participation rate). Forty-nine (53%) participants had EB simplex (EBS), 40 (43%) had dystrophic EB (DEB), and 3 (3%) had junctional EB (JEB). Point prevalence for EB of all types was 19.5 per million, and 10.4, 8.6 and 0.9 per million for EBS, DEB and JEB, respectively. Thirty-four participants had intermediate or severe EB. There were 29 paediatric cases and almost even numbers of males and females. Compared to NZ European and Maori, prevalence rates were lower for Pacific and Asian people and higher in the Middle Eastern/Latin American/African population. Eight out of 14 skin biopsy results were informative, and 14 of 15 genetic test results were informative. CONCLUSION: New Zealand has similar prevalence rates of EB compared with other national cohorts. This is likely to be an underestimate due to methodological limitations. Recent advancements in genomic testing have resulted in an improved diagnostic rate in our population. Further research into ethnic differences in prevalence, and exploring the characteristics of lethal forms of EB, is warranted. A dynamic registry may be helpful for the EB community in NZ.

Features of multiple self-healing squamous epithelioma and Loeys-Dietz syndrome in a patient with a novel TGFBR1 variant.

Multiple self-healing squamous epithelioma (MSSE, Ferguson-Smith disease) and Loeys-Dietz syndrome (LDS) are allelic conditions associated with pathogenic variants in the transforming growth factor beta receptor 1 gene (TGFBR1). We describe a patient with a novel missense variant in this gene: c.664G > A, p.[Gly222Arg], who clinically presents with both syndromes. The patient also has a history of gastric antral vascular ectasia, which has not been reported previously in LDS.

STAC3 variants cause a congenital myopathy with distinctive dysmorphic features and malignant hyperthermia susceptibility.

SH3 and cysteine-rich domain-containing protein 3 (STAC3) is an essential component of the skeletal muscle excitation-contraction coupling (ECC) machinery, though its role and function are not yet completely understood. Here, we report 18 patients carrying a homozygous p.(Trp284Ser) STAC3 variant in addition to a patient compound heterozygous for the p.(Trp284Ser) and a novel splice site change (c.997-1G > T). Clinical severity ranged from prenatal onset with severe features at birth, to a milder and slowly progressive congenital myopathy phenotype. A malignant hyperthermia (MH)-like reaction had occurred in several patients. The functional analysis demonstrated impaired ECC. In particular, KCl-induced membrane depolarization resulted in significantly reduced sarcoplasmic reticulum Ca2+ release. Co-immunoprecipitation of STAC3 with CaV 1.1 in patients and control muscle samples showed that the protein interaction between STAC3 and CaV 1.1 was not significantly affected by the STAC3 variants. This study demonstrates that STAC3 gene analysis should be included in the diagnostic work up of patients of any ethnicity presenting with congenital myopathy, in particular if a history of MH-like episodes is reported. While the precise pathomechanism remains to be elucidated, our functional characterization of STAC3 variants revealed that defective ECC is not a result of CaV 1.1 sarcolemma mislocalization or impaired STAC3-CaV 1.1 interaction.

A Clinical Review of Generalized Overgrowth Syndromes in the Era of Massively Parallel Sequencing.

The overgrowth syndromes are important to diagnose, not just for accurate genetic counseling, but also for knowledge surrounding cancer surveillance and prognosis. There has been a recent expansion in the number of genes associated with a mendelian overgrowth phenotype, so this review updates previous classifications of overgrowth syndromes. We also describe a clinical and molecular approach to the investigation of individuals presenting with overgrowth. This review aims to assist the clinical diagnosis of generalized overgrowth syndromes by outlining the salient features of well-known overgrowth syndromes alongside the many syndromes that have been discovered and classified more recently. We provide key clinical "handles" to aid clinical diagnosis and a list of genes to aid with panel design when using next generation sequencing, which we believe is frequently needed due to the overlapping phenotypic features seen between overgrowth syndromes.

The genetics of recurrent hydatidiform moles: new insights and lessons from a comprehensive analysis of 113 patients.

Hydatidiform mole is an aberrant human pregnancy characterized by early embryonic arrest and excessive trophoblastic proliferation. Recurrent hydatidiform moles are defined by the occurrence of at least two hydatidiform moles in the same patient. Fifty to eighty percent of patients with recurrent hydatidiform moles have biallelic pathogenic variants in NLRP7 or KHDC3L. However, in the remaining patients, the genotypic types of the moles are unknown. We characterized 80 new hydatidiform mole tissues, 57 of which were from patients with no mutations in the known genes, and we reviewed the genotypes of a total of 123 molar tissues. We also reviewed mutation analysis in 113 patients with recurrent hydatidiform moles. While all hydatidiform moles from patients with biallelic NLRP7 or KHDC3L mutations are diploid biparental, we demonstrate that those from patients without mutations are highly heterogeneous and only a small minority of them are diploid biparental (8%). The other mechanisms that were found to recur in patients without mutations are diploid androgenetic monospermic (24%) and triploid dispermic (32%); the remaining hydatidiform moles were misdiagnosed as moles due to errors in the analyses and/or their unusual mechanisms. We compared three parameters of genetic susceptibility in patients with and without mutations and show that patients without mutations are mostly from non-familial cases, have fewer reproductive losses, and more live births. Our data demonstrate that patients with recurrent hydatidiform moles and no mutations in the known genes are, in general, different from those with mutations; they have a milder genetic susceptibility and/or a multifactorial etiology underlying their recurrent hydatidiform moles. Categorizing these patients according to the genotypic types of their recurrent hydatidiform moles may facilitate the identification of novel genes for this entity.

PBX1 haploinsufficiency leads to syndromic congenital anomalies of the kidney and urinary tract (CAKUT) in humans.

BACKGROUND: Congenital anomalies of the kidney and urinary tract (CAKUT) represent a significant healthcare burden since it is the primary cause of chronic kidney in children. CNVs represent a recurrent molecular cause of CAKUT but the culprit gene remains often elusive. Our study aimed to define the gene responsible for CAKUT in patients with an 1q23.3q24.1 microdeletion. METHODS: We describe eight patients presenting with CAKUT carrying an 1q23.3q24.1 microdeletion as identified by chromosomal microarray analysis (CMA). Clinical features were collected, especially the renal and urinary tract phenotype, and extrarenal features. We characterised PBX1 expression and localisation in fetal and adult kidneys using quantitative RT-PCR and immunohistochemistry. RESULTS: We defined a 276-kb minimal common region (MCR) that only overlaps with the PBX1 gene. All eight patients presented with syndromic CAKUT. CAKUT were mostly bilateral renal hypoplasia (75%). The most frequent extrarenal symptoms were developmental delay and ear malformations. We demonstrate that PBX1 is strongly expressed in fetal kidneys and brain and expression levels decreased in adult samples. In control fetal kidneys, PBX1 was localised in nuclei of medullary, interstitial and mesenchymal cells, whereas it was present in endothelial cells in adult kidneys. CONCLUSIONS: Our results indicate that PBX1 haploinsufficiency leads to syndromic CAKUT as supported by the Pbx1-null mice model. Correct PBX1 dosage appears to be critical for normal nephrogenesis and seems important for brain development in humans. CMA should be recommended in cases of fetal renal anomalies to improve genetic counselling and pregnancy management.

Recurrent de novo BICD2 mutation associated with arthrogryposis multiplex congenita and bilateral perisylvian polymicrogyria.

Autosomal dominantly inherited mutations of BICD2 are associated with congenital-onset spinal muscular atrophy characterised by lower limb predominance. A few cases have also showed upper motor neuron pathology, including presenting with features resembling hereditary spastic paraplegia. The age-of-onset for the published families is usually at birth but also included cases with childhood- and adult-onset disease. In this report we described two isolated probands that presented in utero with features associated with reduced fetal movements. Both cases were diagnosed at birth with arthrogryposis multiplex congenita (AMC) and hypotonia. Other variable features included congenital fractures, hip dislocation, micrognathia, respiratory insufficiency, microcephaly and bilateral perisylvian polymicrogyria. Patient 1 is 4 years of age and stable, but shows significant motor developmental delay and delayed speech. Patient 2 passed away at 7 weeks of age. Through next generation sequencing we identified the same missense substitution in BICD2 (p.Arg694Cys) in both probands. Sanger sequencing showed that in both cases the mutation arose de novo. The in utero onset in both cases suggests that the p.Arg694Cys substitution may have a more deleterious effect on BICD2 function than previously described mutations. Our results broaden the phenotypes associated with BICD2 mutations to include AMC and cortical malformations and therefore to a similar phenotypic spectrum to that associated with its binding partner DYNC1H1.

Loss-of-function mutations in SMARCE1 cause an inherited disorder of multiple spinal meningiomas.

One-third of all primary central nervous system tumors in adults are meningiomas. Rarely, meningiomas occur at multiple sites, usually occurring in individuals with type 2 neurofibromatosis (NF2). We sequenced the exomes of three unrelated individuals with familial multiple spinal meningiomas without NF2 mutations. We identified two individuals with heterozygous loss-of-function mutations in the SWI/SNF chromatin-remodeling complex subunit gene SMARCE1. Sequencing of SMARCE1 in six further individuals with spinal meningiomas identified two additional heterozygous loss-of-function mutations. Tumors from individuals with SMARCE1 mutations were of clear-cell histological subtype, and all had loss of SMARCE1 protein, consistent with a tumor suppressor mechanism. Our findings identify multiple-spinal-meningioma disease as a new discrete entity and establish a key role for the SWI/SNF complex in the pathogenesis of both meningiomas and tumors with clear-cell histology.