Mosaic Muir Torre Syndrome: Keratoacanthoma as a Piece of the Puzzle.

ABSTRACT: Lynch syndrome is an inherited condition, which increases the risk of numerous visceral malignancies and cutaneous tumors such as keratoacanthomas and sebaceous tumors. It is typically identified by immunohistochemistry of tissue taken from tumors or through genetic testing with next-generation sequencing. Diagnosing Lynch syndrome becomes more complex when the individual is mosaic for the relevant pathogenic variant. There are very few cases of this reported in the medical literature. It is even more unusual for the diagnosis to be made based on testing of a keratoacanthoma lesion. We report a case where immunohistochemistry of a keratoacanthoma helped make a diagnosis of mosaic Lynch syndrome. We will explore how mosaicism should be considered when a phenotype is strong, even if next-generation sequencing reports no pathogenic or likely pathogenic variant and how lesions such as keratoacanthomas can have a role in the early detection and treatment of future malignancies.

Familial Bainbridge-Ropers syndrome: Report of familial ASXL3 inheritance and a milder phenotype.

De novo truncating and splicing pathogenic variants in the Additional Sex Combs-Like 3 (ASXL3) gene are known to cause neurodevelopmental delay, intellectual disability, behavioral difficulties, hypotonia, feeding problems and characteristic facial features. We previously reported 45 patients with ASXL3-related disorder including three individuals with a familial variant. Here we report the detailed clinical and molecular characteristics of these three families with inherited ASXL3-related disorder. First, a father and son with c.2791_2792del p.Gln931fs pathogenic variant. The second, a mother, daughter and son with c.4534C > T, p.Gln1512Ter pathogenic variant. The third, a mother and her daughter with c.4441dup, p.Leu1481fs maternally inherited pathogenic variant. This report demonstrates intrafamilial phenotypic heterogeneity and confirms heritability of ASXL3-related disorder.

SDHC phaeochromocytoma and paraganglioma: A UK-wide case series.

OBJECTIVE: Phaeochromocytomas and paragangliomas (PPGL) are rare, but strongly heritable tumours. Variants in succinate dehydrogenase (SDH) subunits are identified in approximately 25% of cases. However, clinical and genetic information of patients with SDHC variants are underreported. DESIGN: This retrospective case series collated data from 18 UK Genetics and Endocrinology departments. PATIENTS: Both asymptomatic and disease-affected patients with confirmed SDHC germline variants are included. MEASUREMENTS: Clinical data including tumour type and location, surveillance outcomes and interventions, SDHC genetic variant assessment, interpretation, and tumour risk calculation. RESULTS: We report 91 SDHC cases, 46 probands and 45 non-probands. Fifty-one cases were disease-affected. Median age at genetic diagnosis was 43 years (range: 11-79). Twenty-four SDHC germline variants were identified including six novel variants. Head and neck paraganglioma (HNPGL, n = 30, 65.2%), extra-adrenal paraganglioma (EAPGL, n = 13, 28.2%) and phaeochromocytomas (PCC) (n = 3, 6.5%) were present. One case had multiple PPGLs. Malignant disease was reported in 19.6% (9/46). Eight cases had non-PPGL SDHC-associated tumours, six gastrointestinal stromal tumours (GIST) and two renal cell cancers (RCC). Cumulative tumour risk (95% CI) at age 60 years was 0.94 (CI: 0.79-0.99) in probands, and 0.16 (CI: 0-0.31) in non-probands, respectively. CONCLUSIONS: This study describes the largest cohort of 91 SDHC patients worldwide. We confirm disease-affected SDHC variant cases develop isolated HNPGL disease in nearly 2/3 of patients, EAPGL and PCC in 1/3, with an increased risk of GIST and RCC. One fifth developed malignant disease, requiring comprehensive lifelong tumour screening and surveillance.

Expanding the phenotype of ASXL3-related syndrome: A comprehensive description of 45 unpublished individuals with inherited and de novo pathogenic variants in ASXL3.

The study aimed at widening the clinical and genetic spectrum of ASXL3-related syndrome, a neurodevelopmental disorder, caused by truncating variants in the ASXL3 gene. In this international collaborative study, we have undertaken a detailed clinical and molecular analysis of 45 previously unpublished individuals with ASXL3-related syndrome, as well as a review of all previously published individuals. We have reviewed the rather limited functional characterization of pathogenic variants in ASXL3 and discuss current understanding of the consequences of the different ASXL3 variants. In this comprehensive analysis of ASXL3-related syndrome, we define its natural history and clinical evolution occurring with age. We report familial ASXL3 pathogenic variants, characterize the phenotype in mildly affected individuals and discuss nonpenetrance. We also discuss the role of missense variants in ASXL3. We delineate a variable but consistent phenotype. The most characteristic features are neurodevelopmental delay with consistently limited speech, significant neuro-behavioral issues, hypotonia, and feeding difficulties. Distinctive features include downslanting palpebral fissures, hypertelorism, tubular nose with a prominent nasal bridge, and low-hanging columella. The presented data will inform clinical management of individuals with ASXL3-related syndrome and improve interpretation of new ASXL3 sequence variants.

Genetics for paediatric radiologists.

An understanding of genetics and genomics is increasingly important for all clinicians. Next-generation genomic sequencing technologies enable sequencing of the entire human genome in short timescales, and are increasingly being implemented in health care systems. Clinicians across all medical specialties will increasingly use results generated from genomic testing to inform their clinical practice and provide the best quality of care for patients. These innovations are already transforming the diagnostic pathways for rare genetic diseases, including skeletal dysplasias, with an inevitable impact on the traditional roles of diagnosticians. This article covers the fundamentals of human genetics, mechanisms of genetic variation and the technologies used to investigate the genetic basis of disease, with a specific focus on skeletal dysplasias and the potential impact of genomics on paediatric radiology.

Expanding the molecular basis and phenotypic spectrum of ZDHHC9-associated X-linked intellectual disability.

Pathogenic variants in Zinc Finger DHHC-Type Containing 9 (ZDHHC9) gene have been identified as the cause of X-linked intellectual disability (XLID) in a small number of families. There are a total of 11 reported pathogenic variants in ZDHHC9 in the literature. The majority of reported variants are familial point mutations. There is one report of XLID associated with a de novo mutation in ZDHHC9, and one family with intragenic deletion within ZDHHC9 detected by array CGH. Although initial reports of families with ZDHHC9 pathogenic variants suggested a nonsyndromic XLID, more recent reports suggest a syndromic phenotype with facial dysmorphism. Here we report four patients with pathogenic variants in ZDHHC9, a family with two siblings and their maternal uncle who presented with XLID due to intragenic deletion of ZDHHC9 detected by array CGH and an 11-year-old boy with a de novo pathogenic missense variant in ZDHHC9, which is the first recurrent ZDHHC9 mutation. Our patients had some distinctive facial features in common, including elongated and down-slanting palpebral fissures and high hairline. Marfanoid habitus and seizures that have been previously reported in association with pathogenic variants in ZDHHC9 were absent in our cohort. Clinical information on patients with ZDHHC9-associated XLID is very scarce. New reports of families with detailed clinical description will add to the existing knowledge and help understand the condition better.

Amniotic band sequence in vascular Ehlers-Danlos Syndrome (EDS): Experience of the EDS National Diagnostic Services in the UK.

The association between vascular Ehlers-Danlos Syndrome (vEDS) and amniotic band sequence (ABS) has been previously reported in the literature, mostly in single patient case reports. Here, we aim to extend the current knowledge of this association through a case series of five unrelated individuals with ABS in association with molecularly confirmed vEDS, in addition to undertaking a comprehensive literature review. All the individuals were recruited through the EDS national diagnostic service in the UK following appropriate history, physical examination and genetic investigations. Clinical presentation ranged from a single constriction ring to complex craniofacial clefts to limb reduction deformities, reflecting the spectrum of ABS presentation. vEDS was inherited paternally (n = 2), maternally (n = 2) and de novo (n = 1). Previously, maternal vEDS was considered the risk factor for ABS, but our findings suggest that it may be the disease status of the fetus which poses the main risk. It is established that amniotic membrane is derived from fetal tissue, which supports our conclusions. Our observations suggest the increased risk of ABS in fetuses with vEDS. Therefore, exploring family history and features that may suggest vEDS diagnosis in patients with ABS might be useful. We also recommend that a collaborative international study would be useful to help gain a better insight into this association.

The Imbalance in Medico-Legal Cover Awareness and Uptake Between Overseas Junior Doctors and Local Graduates in the NHS.

Background Recent reports showed that overseas doctors were more likely than UK graduates to be referred by their employers to the General Medical Council (GMC). We investigated the trend of medico-legal insurance awareness and uptake of medical defence organisations (MDOs) by junior doctors and to examine if there is a difference between overseas and UK graduates. Methods Online questionnaire survey sent to junior doctors within the Yorkshire and Humber Deanery. Data regarding year of graduation, country of origin of primary medical qualification, year of starting work in the National Health Service (NHS) and date of joining an MDO were collected. Participant-identifiable information was not collected. Results A total of 202 junior doctors completed the survey: 153 (76%) UK graduates and 49 (24%) overseas. Overseas doctors were less likely to know about MDO compared to UK graduates prior to working in the NHS (13 [26.5%] vs. 146 [95.4%]; p < 0.0001). At the time of starting practice, MDO uptake was still significantly lower amongst overseas graduates (4 [8.2%] vs. 144 [94.1%]; p < 0.0001). Uptake by overseas doctors increased after starting work to 33 (67.3%). However, despite improvement in MDO uptake, a significant number of overseas doctors still did not have independent cover compared with UK graduates (16 [32.7%] vs. 3 [2%]; p < 0.0001). Conclusions Overseas graduates joining the NHS are still less likely to be aware of the requirement of adequate medico-legal cover and are less likely to join an MDO compared with UK graduates. Healthcare providers and regulators should work to decrease the existing gap and increase awareness amongst newly arrived overseas doctors.

Homozygosity for the pathogenic RET hotspot variant p.Cys634Trp: A consanguineous family with MEN2A.

Multiple endocrine neoplasia type 2 (MEN2) is a dominantly inherited condition with defined correlations between the genetic variant and clinical presentations. The location of pathogenic variants in the RET gene is a significant determinant of disease presentation and is associated with variable gene activation. Heterozygous pathogenic variants in codon 634 result in earlier onset of medullary thyroid carcinoma and higher incidence of phaeochromocytoma. Here we describe a consanguineous family with MEN2A that includes two children homozygous for the established pathogenic variant p. Cys634Trp. Both parents and a sibling were confirmed to being heterozygotes. Previous reports of biallelic or multiple RET variants have been limited to weakly activating variants. We present the first report of individuals homozygous for the highly activating RET p. Cys634Trp pathogenic variant and discuss disease severity and onset in this rare occurrence.

Homozygous intronic variants in TPM2 cause recessively inherited Escobar variant of multiple pterygium syndrome and congenital myopathy.

Pathogenic variants in TPM2 have been associated with a variable clinical spectrum, including congenital myopathies and distal arthrogryposis, all but one with dominant inheritance. We report the second case of recessively inherited TPM2-related Escobar variant of multiple pterygium syndrome and congenital myopathy in a patient from a consanguineous family. Ultra-structural examination of the biopsy revealed few cores/mini-cores and sparse nemaline rods. We found a novel homozygous intronic sequence variant, c.564-2A>C in TPM2. This variant is predicted to abolish the consensus acceptor splice site for exon 6b of TPM2 gene. Parents of the proband, both healthy adults with no clinical features, were heterozygous for the variant. Here we establish a homozygous intronic variant in TPM2 as the likely cause of Escobar variant of multiple pterygium syndrome and congenital myopathy, with sparse nemaline rods.

DSE associated musculocontractural EDS, a milder phenotype or phenotypic variability.

Musculocontractural Ehlers-Danlos syndrome (mcEDS) is an autosomal recessive condition characterized by distinct craniofacial features, multisystem congenital malformations and progressive fragility of connective tissues. It is caused by pathogenic variants in CHST14 and DSE genes. There are three reports of pathogenic variants in DSE in four mcEDS patients. In this study we provide clinical and molecular presentation of two new patients with DSE related mcEDS. Analysing clinical exome data, a homozygous pathogenic DSE variant, c.1150_1157del p.(Pro384Trpfs*9), was identified in a 32 year old man with bilateral congenital talipes equinovarus, characteristic facial features, myopia, hyperextensible skin at the elbows, significant palmar wrinkling, bilateral inguinal hernias and chronic leg, back and joint pain. Electron microscopical examination of skin biopsy showed changes consistent with mild compensatory elastic fibre hypertrophy and mildly loose collagen bundles. The variant is predicted to result in a frameshift and introduction of a premature termination codon in the final exon of the DSE gene, anticipated to lead to the loss of approximately 60% of the normal reading frame. The second patient has a phenotype consistent with previously reported cases of DSE associated musculocontractural EDS. A novel homozygous missense DSE variant of uncertain clinical significance was detected. This case study further delineates the DSE associated mcEDS phenotype and illustrates absence of major cutaneous, cardiovascular, renal and respiratory features, which supports previous suggestions that patients with DSE associated mcEDS present with a milder phenotype compared to those with CHST14 mutations.

Mosaicism in ASXL3-related syndrome: Description of five patients from three families.

De novo pathogenic variants in the additional sex combs-like 3 (ASXL3) gene cause a rare multi-systemic neurodevelopmental disorder. There is growing evidence that germline and somatic mosaicism are more common and play a greater role in genetic disorders than previously acknowledged. There is one previous report of ASXL3-related syndrome caused by de novo pathogenic variants in two siblings suggesting gonadal mosaicism. In this report, we present five patients with ASXL3-related syndrome, describing two families comprising two non-twin siblings harbouring apparent de novo pathogenic variants in ASXL3. Parents were clinically unaffected and there was no evidence of mosaicism from genomic DNA on exome-trio data, suggesting germline mosaicism in one of the parents. We also describe clinical details of a patient with typical features of ASXL3-related syndrome and mosaic de novo pathogenic variant in ASXL3 in 30-35% of both blood and saliva sample on trio-exome sequencing. We expand the known genetic basis of ASXL3-related syndromes and discuss mosaicism as a disease mechanism in five patients from three unrelated families. The findings of this report highlight the importance of taking gonadal mosaicism into consideration when counselling families regarding recurrence risk. We also discuss postzygotic mosaicism as a cause of fully penetrant ASXL3-related syndrome.

Exploring the association between SRPX2 variants and neurodevelopment: How causal is it?

The SRPX2 gene (Sushi-repeat-containing protein, X-linked, 2, OMIM*300642), located on Xq22.1, encodes a secreted protein that is highly expressed in neurons of cerebral cortex. SRPX2 was first implicated in neurodevelopment, learning and rolandic seizure when two patients with potentially pathogenic variants, c.980A>G (p.Asn327Ser) and c.215A>C (p.Tyr72Ser), in SRPX2 gene were identified. Subsequent experimental studies demonstrated that SRPX2 is needed for vocalization and synapse formation in mice, and that both silencing SRPX2 and injecting (p.Asn327Ser) in mouse models results in alteration in neuronal migration in cerebral cortex and epilepsy. A number of studies demonstrated that SRPX2 interacts with FOXP2 (Foxhead box protein P2), a gene responsible for speech and language disorder, and that FoxP2 controls timing and level of expression of SRPX2. Despite the supportive evidence for the role of SRPX2 in speech and language development and disorders, there are questions over its definitive association with neurodevelopmental disorders and epilepsy. In this paper, the role of SRPX2 as one in a network of many genes involved in speech and language is discussed. The goal of this paper is to examine the role of SRPX2 variants through describing two patients with potentially pathogenic variants in SRPX2, c.751G>C (p.Ala251Pro) and c.762G>T (p.Lys254Asn) presenting with language and motor delay, intellectual disability as well as congenital anomalies. We explore the contribution of SRPX2 variants to clinical phenotype in our patients and conclude that these variants at least partially explain the phenotype. Further studies are necessary to establish and confirm the association between SRPX2 and neurodevelopment particularly speech and language development.

Duplications of GPC3 and GPC4 genes in symptomatic female carriers of Simpson-Golabi-Behmel syndrome type 1.

GPC3 and GPC4 are the only two genes in which mutations are known to cause Simpson-Golabi-Behmel syndrome type 1 (SGBS1). The majority of SGBS1 patients have point mutations or deletions in GPC3. Only one SGBS1 family has been reported with duplication of both GPC3 and GPC4. Although clinical presentation of SGBS1 in affected males is well defined, the phenotype in female carriers is less clear. In total, six female carriers with clinical expression of SGBS1 have been reported to date. In this study, we provide description of two families with rare duplications in both GPC3 and GPC4. These imbalances resulted in SGBS1 in males, while female carriers with skewed X-inactivation exhibited significant features of SGBS1 including congenital heart defect, hernias, intellectual disability and coarse facial features. In family 2, a SGBS diagnosis was not considered in the father until after the diagnosis had been first considered and made in the affected daughter. We emphasize on the importance of testing at risk females and careful examination of those who are found to be carriers of SGBS1. We also discuss and provide supportive evidence for the role of skewed X-inactivation in clinical expression of SGBS1 in female carriers.

Aortic aneurysm/dissection and osteogenesis imperfecta: Four new families and review of the literature.

Osteogenesis imperfecta (OI) is the commonest form of heritable bone fragility. It is mainly characterized by fractures, hearing loss and dentinogenesis imperfecta. OI patients are at increased risk of cardiovascular disease of variable severity. Aortic aneurysm/dissection is one of the rarer but potentially serious cardiovascular complications of OI. So far, only six patients with aortic dissection and OI have been reported. As such, present OI diagnostic guidelines do not recommend systematic screening of patients for aortopathy. Here, we report on the clinical and molecular characteristics of three new OI patients and one additional patient with a first degree relative who presented with aortic dissection and/or aneurysm surgery. This observation further opens up the discussion on the need for and extent of cardiovascular screening in adult patients with OI.

Clinical and molecular characterization of the first familial report of 1p32 microdeletion.

Structural rearrangements of chromosome band 1p31p32 are rare, and their phenotypic consequences remain poorly delineated. Up to 12 patients with learning difficulties, developmental delay, multiple congenital anomalies and microdeletion of the chromosome band 1p31p32 have been described. Inheritance of this deletion has not been reported previously. We describe the inheritance of the 1p32 deletion and discuss the relevance of this deletion to the described phenotype. The differences in clinical and molecular characteristics between the proband and other published reports are reviewed. Patients were evaluated in Genetics Clinic with history, examination and investigation. The existing literature on interstitial deletions of 1p was reviewed. Here, we report on a three-generation family, where the index patient was an adult female with learning difficulty, dysmorphic features, microcephaly, ambiguous genitalia, congenital hip dislocation and brachydactyly in whom a maternally inherited 1.45 Mbp interstitial deletion was detected at 1p32.3. Both her mother and maternal grandmother have learning difficulties and dysmorphic features. There are 14 OMIM genes in the deleted region including LRP8 and DMRTB1. The NFIA gene is not deleted in this family. The first report of a familial 1p32 microdeletion in three generations of a family carrying the smallest reported a deletion involving this region and brachydactyly as a previously unreported feature.

Carbamazepine Improves Apneic Episodes in Congenital Central Hypoventilation Syndrome (CCHS) With a Novel PHOX2B Exon 1 Missense Mutation.

ABSTRACT: Pathogenic variants in Paired-Like Homeobox 2B (PHOX2B) gene cause congenital central hypoventilation syndrome (CCHS), a rare disorder of the nervous system characterized by absent or reduced ventilatory response to hypoxia and hypercapnia. The focus of management in CCHS is optimizing ventilation. Thus far, no medication has proved effective in improving ventilation. Most CCHS cases are caused by polyalanine repeat expansion mutations. Non-polyalanine repeat expansion mutations are the cause in 8% of cases and result in a more severe clinical presentation. PHOX2B has 3 exons. Exon 3 of PHOX2B is the most common location for CCHS-causing mutations. Thus far, only 9 CCHS-causing mutations have been reported in exon 1, 8 of which were nonsense mutations. We report a child with CCHS who was found to have a novel heterozygous missense variant in exon 1; c.95A > T. Improvement in his apneic episodes was observed following treatment with carbamazepine.