Search

With the increasing availability and clinical use of exome and whole-genome sequencing, reverse phenotyping is now becoming common practice in clinical genetics. Here, we report a patient identified through the Wellcome Trust Deciphering Developmental Disorders study who has homozygous pathogenic variants in CC2D2A and a de-novo heterozygous pathogenic variant in KIDINS220. He presents with developmental delay, intellectual disability, and oculomotor apraxia. Reverse phenotyping has demonstrated that he likely has a composite phenotype with contributions from both variants. The patient is much more mildly affected than those with Joubert Syndrome or Spastic paraplegia, intellectual disability, nystagmus, and obesity, the conditions associated with CC2D2A and KIDINS220 respectively, and therefore, contributes to the phenotypic variability associated with the two conditions.

Autism spectrum disorder (ASD) encompasses a spectrum of pervasive neuropsychiatric disorders characterized by deficits in social interaction, communication, unusual and repetitive behaviours. The aetiology of ASD is believed to involve complex interactions between genetic and environmental factors; it can be further classified as syndromic or nonsyndromic, according to whether it is the primary diagnosis or secondary to an existing condition where both common and rare genetic variants contribute to the development of ASD or are clearly causal. The prevalence of ASD in children is increasing with higher rates of diagnosis and an estimated one in 100 affected in the UK. Given that heritability is a major contributing factor, we aim to discuss research findings to-date in the context of a high-risk autism candidate gene, SHANK3 (SH3 and multiple ankyrin repeat domain 3), with its loss resulting in synaptic function disruption. We present a 10-year-old patient with a pathogenic de novo heterozygous c.1231delC, p.Arg411Val frameshift variant in SHANK3. He presented with severe autism, attention deficit hyperactivity disorder and pathological demand avoidance, on a background of developmental impairment and language regression. The number of genes associated with autism is ever increasing. It is a heterogeneous group of disorders with no single gene conferring pathogenesis in the majority of cases. Genetic abnormalities can be detected in ~15% of ASD and these range from copy number variants in 16p11.2 and 15q13.2q13.3 to several well-known genetic disorders including tuberous sclerosis and fragile X syndrome. Further, high confidence autism genes include but are not limited to NRXN, NLGN3, NLGN4, SHANK2 and SHANK3.

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 OI-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.

Type V osteogenesis imperfecta (OI) presents with moderate-to-severe skeletal deformity and is characterized by hyperplastic callus formation at fracture sites and calcification of the interosseous membranes of the forearm and lower leg. The facial dysmorphism is not well characterized and has not been described in previous reports. Inheritance is autosomal dominant, although the genetic aetiology remained unknown until very recently. The aims of this study were to establish the genetic aetiology in patients with type V OI and further characterize patients with this condition, and to ascertain whether they have a similar clinical phenotype and facial dysmorphism. Three families (one mother-daughter pair and two singletons) were identified with the above features and further investigations (molecular genetic analysis and skin biopsy including electron microscopy, histology and collagen species analysis) were performed. Accurate phenotyping of patients with type V OI was performed. PCR amplification was performed using the Sheffield Diagnostic Genetics Service pyrosequencing assay for the interferon-induced transmembrane protein-5 (IFITM5) gene. All the patients had been confirmed to have a heterozygous variant, c.[-14C>T];[=], in the 5'-UTR of the IFITM5 gene, which is located in the transcribed region of this gene. This recurrent mutation, in IFITM5, also known as bone-restricted interferon-induced transmembrane protein-like protein or BRIL, encodes a protein with a function in bone formation and plays an important role in osteoblast formation. All four patients in this study appear to have similar clinical features and facial dysmorphism, including a short, up-turned nose, a small mouth, a prominent chin and greyish-blue sclerae. Skin biopsy in one patient showed clumping of elastic fibres and normal biochemical analysis of collagen. We have been able to characterize patients with type V OI further and confirm the genetic aetiology in this distinct form of OI. Accurate phenotyping (including describing the common facial features) before investigations is important to enable the useful interpretation of genetic results and/or target-specific gene testing.

Duplications of 18p have been reported in the literature associated with a range of different abnormalities and also in patients with normal phenotypes. The majority of these reports are based solely on G-banded cytogenetic evaluation. The use of arrayCGH characterization has improved the ability to define regions of imbalance and is helping to identify potential underlying triplosufficiency of any duplicated genes. We report on a family where the father and his two daughters all have a duplication 18p11.32-p11.31 characterized by microarray. They present with variable levels of intellectual disability/developmental delay and behavioural difficulties without any physical anomalies. This family contributes toward the growing knowledge of pure duplications of 18p and provides information on interpretation of novel array findings in the context of family history. It also reiterates the importance of elucidating a detailed learning and developmental phenotype and family pedigree in aiding interpretation of genetic testing results.

We report a fetus with mosaic trisomy 11 who also had bilateral renal agenesis. We describe the post-mortem examination findings in the fetus and cytogenetic analysis. There are no earlier reports of full trisomy 11, presumably because it is lethal and results in early spontaneous miscarriages. There is only one report published earlier in a fetus with mosaic trisomy 11. There have been a few case reports of trisomy 11 identified in pre-natal samples, where it was associated with normal outcome. Bilateral renal agenesis has not been reported earlier in association with mosaic nor non-mosaic trisomy 11. We describe this rare cytogenetic finding in a fetus with bilateral renal agenesis. We also discuss the issues around genetic counselling when this is encountered in clinical practice.

Osteogenesis imperfecta (OI) is a heterogeneous group of inherited disorders of bone formation, resulting in low bone mass and an increased propensity for fractures. It is a variable condition with a range of clinical severities. The histological and ultrastructural findings in the skin of patients with OI have not been described in detail in the previously published literature. Although protein analysis of cultured fibroblasts has historically been used in the diagnostic work-up of OI patients, other aspects of skin examination are not routinely performed as part of the diagnostic pathway in patients with OI. The aims of this study were to perform histological and ultrastructural examination of skin biopsies in patients with OI. This was to identify common and distinguishing features in the numerous genetically distinct subtypes of OI and compare the findings with those in patients who did not present with fractures, and to enable the use of the results thus obtained to aid in the diagnostic work-up of patients with OI. As part of a larger research study set-up to identify clinical features and natural history in patients with atypical features of OI, skin biopsy and examination (histology and electron microscopy) were undertaken. Genetic analysis and ancillary investigations were also performed to identify similarities within this group and to differentiate this group from the 'normal' population. At the end of this study, we were able to demonstrate that the histological and electron microscopic findings on a skin biopsy may be an indicator of the likelihood of identifying a pathogenic mutation in type 1 collagen genes. This is because patients with specific findings on examination, such as elastic fibre area fraction (on histological analysis), collagen fibril diameter variability, deviation from the expected mean and collagen flowers (on electron microscopy), are more likely to be positive on genetic analyses. This has, in turn, provided more insight into the pathways to direct gene testing and has reinforced the need for accurate phenotyping before undertaking further genetic investigations. The morphometric assessment of elastic fibre area fraction and ultrastructural findings from this study have provided us with a better understanding of OI and insights into the possible mechanism of these changes in the skin. Correlation of skin findings with the clinical phenotype as well as genetic testing has enabled understanding of the molecular pathogenesis and translation of changes at the genomic level to clinical phenotype.

Zimmerman–Laband syndrome is a rare genetic disorder characterized by gingival fibromatosis, dysplastic or absent nails, hypoplasia of the distal phalanges, scoliosis, hepatosplenomegaly, hirsutism and abnormalities of the cartilage of nose and/or ears. We would like to give an update on the progres