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Clinical Dysmorphology Jul 2020The clinical phenotype of 1q21.1 microdeletion syndrome is highly heterogeneous. It is characterized by dysmorphic facial features, microcephaly, and developmental... (Review)
Review
The clinical phenotype of 1q21.1 microdeletion syndrome is highly heterogeneous. It is characterized by dysmorphic facial features, microcephaly, and developmental delay. Several congenital defects, including cardiac, ocular, skeletal anomalies, and psychiatric or behavioural abnormalities, have also been described. Here, we report on two siblings with substantial intrafamilial phenotypic variability carrying a heterozygous deletion of the 1q21.1 region spanning a known critical genomic area (~1.35 Mb). The microdeletion was inherited from the unaffected father. Patients described here show a spectrum of clinical features, a portion of which overlap with those previously reported in patients with 1q21.1 microdeletions. In addition, we review the clinical reports of 66 individuals with this condition. These findings extend and substantiate the current clinical understanding of recurrent copy number variations in the 1q21.1 region.
Topics: Abnormalities, Multiple; Adult; Chromosome Deletion; Chromosome Duplication; Chromosomes, Human, Pair 1; DNA Copy Number Variations; Family; Female; Heart Defects, Congenital; Humans; India; Intellectual Disability; Male; Megalencephaly; Microcephaly; Pedigree; Phenotype; Syndrome
PubMed: 32459673
DOI: 10.1097/MCD.0000000000000327 -
International Journal of Molecular... May 2024Macrocephaly, characterized by an abnormally large head circumference, often co-occurs with distinctive finger changes, presenting a diagnostic challenge for clinicians.... (Review)
Review
Macrocephaly, characterized by an abnormally large head circumference, often co-occurs with distinctive finger changes, presenting a diagnostic challenge for clinicians. This review aims to provide a current synthetic overview of the main acquired and genetic etiologies associated with macrocephaly and finger changes. The genetic cause encompasses several categories of diseases, including bone marrow expansion disorders, skeletal dysplasias, ciliopathies, inherited metabolic diseases, RASopathies, and overgrowth syndromes. Furthermore, autoimmune and autoinflammatory diseases are also explored for their potential involvement in macrocephaly and finger changes. The intricate genetic mechanisms involved in the formation of cranial bones and extremities are multifaceted. An excess in growth may stem from disruptions in the intricate interplays among the genetic, epigenetic, and hormonal factors that regulate human growth. Understanding the underlying cellular and molecular mechanisms is important for elucidating the developmental pathways and biological processes that contribute to the observed clinical phenotypes. The review provides a practical approach to delineate causes of macrocephaly and finger changes, facilitate differential diagnosis and guide for the appropriate etiological framework. Early recognition contributes to timely intervention and improved outcomes for affected individuals.
Topics: Humans; Megalencephaly; Fingers
PubMed: 38791606
DOI: 10.3390/ijms25105567 -
Nature Genetics Jun 2012Megalencephaly-capillary malformation (MCAP) and megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) syndromes are sporadic overgrowth disorders associated...
Megalencephaly-capillary malformation (MCAP) and megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) syndromes are sporadic overgrowth disorders associated with markedly enlarged brain size and other recognizable features. We performed exome sequencing in 3 families with MCAP or MPPH, and our initial observations were confirmed in exomes from 7 individuals with MCAP and 174 control individuals, as well as in 40 additional subjects with megalencephaly, using a combination of Sanger sequencing, restriction enzyme assays and targeted deep sequencing. We identified de novo germline or postzygotic mutations in three core components of the phosphatidylinositol 3-kinase (PI3K)-AKT pathway. These include 2 mutations in AKT3, 1 recurrent mutation in PIK3R2 in 11 unrelated families with MPPH and 15 mostly postzygotic mutations in PIK3CA in 23 individuals with MCAP and 1 with MPPH. Our data highlight the central role of PI3K-AKT signaling in vascular, limb and brain development and emphasize the power of massively parallel sequencing in a challenging context of phenotypic and genetic heterogeneity combined with postzygotic mosaicism.
Topics: Class I Phosphatidylinositol 3-Kinases; Exome; Germ-Line Mutation; Humans; Hydrocephalus; Malformations of Cortical Development; Megalencephaly; Mutation; Mutation, Missense; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Syndrome
PubMed: 22729224
DOI: 10.1038/ng.2331 -
Journal of the Belgian Society of... 2021The main differential diagnosis of leukodystrophy associated with macrocephaly consists of Alexander disease, Canavan disease, and megalencephalic leukodystrophy with...
The main differential diagnosis of leukodystrophy associated with macrocephaly consists of Alexander disease, Canavan disease, and megalencephalic leukodystrophy with subcortical cysts. Distinguishing imaging characteristics of Alexander disease are an apicoposterior gradient of white matter involvement and a periventricular T2-hypointense rim.
PubMed: 34723085
DOI: 10.5334/jbsr.2588 -
Human Molecular Genetics Oct 2023Rab GTPases are important regulators of intracellular vesicular trafficking. RAB5C is a member of the Rab GTPase family that plays an important role in the endocytic...
Rab GTPases are important regulators of intracellular vesicular trafficking. RAB5C is a member of the Rab GTPase family that plays an important role in the endocytic pathway, membrane protein recycling and signaling. Here we report on 12 individuals with nine different heterozygous de novo variants in RAB5C. All but one patient with missense variants (n = 9) exhibited macrocephaly, combined with mild-to-moderate developmental delay. Patients with loss of function variants (n = 2) had an apparently more severe clinical phenotype with refractory epilepsy and intellectual disability but a normal head circumference. Four missense variants were investigated experimentally. In vitro biochemical studies revealed that all four variants were damaging, resulting in increased nucleotide exchange rate, attenuated responsivity to guanine exchange factors and heterogeneous effects on interactions with effector proteins. Studies in C. elegans confirmed that all four variants were damaging in vivo and showed defects in endocytic pathway function. The variant heterozygotes displayed phenotypes that were not observed in null heterozygotes, with two shown to be through a dominant negative mechanism. Expression of the human RAB5C variants in zebrafish embryos resulted in defective development, further underscoring the damaging effects of the RAB5C variants. Our combined bioinformatic, in vitro and in vivo experimental studies and clinical data support the association of RAB5C missense variants with a neurodevelopmental disorder characterized by macrocephaly and mild-to-moderate developmental delay through disruption of the endocytic pathway.
Topics: Animals; Humans; Child; Zebrafish; Caenorhabditis elegans; Neurodevelopmental Disorders; Intellectual Disability; Phenotype; rab GTP-Binding Proteins; Megalencephaly; Developmental Disabilities; Mutation, Missense; rab5 GTP-Binding Proteins
PubMed: 37552066
DOI: 10.1093/hmg/ddad130 -
Medicina 2018In a wide spectrum of cases in childhood, macrocephaly does not carry a neurological risk, although a range of possibilities will have an impact on both the evolutionary...
In a wide spectrum of cases in childhood, macrocephaly does not carry a neurological risk, although a range of possibilities will have an impact on both the evolutionary and cognitive aspects of children. The previous happens in pathologies with progressive components, such as tumors or hydrocephalus, and in those cases in which the factor of the growth of the cephalic perimeter is given by structural components of the nervous system as it happens in megalocephaly. As in all other medical acts, the careful taking of the anamnesis, the appropriate neurological examination and the valuations of the neurodevelopment items can give a thorough orientation about the etiology and importance of the problem. The help of diagnostic aids as well as images will provide the other data to define the diagnosis and propose a treatment.
Topics: Child; Diagnosis, Differential; Humans; Hydrocephalus; Megalencephaly
PubMed: 30199374
DOI: No ID Found -
Science Advances Mar 2023Pathogenic variants in , a lysine methyltransferase, are associated with global developmental delay, macrocephaly, autism, and congenital anomalies (OMIM 617788). Given...
Pathogenic variants in , a lysine methyltransferase, are associated with global developmental delay, macrocephaly, autism, and congenital anomalies (OMIM 617788). Given the relatively recent discovery of this disorder, it has not been fully characterized. Deep phenotyping of the largest ( = 43) patient cohort to date identified that hypotonia and congenital heart defects are prominent features that were previously not associated with this syndrome. Both missense variants and putative loss-of-function variants resulted in slow growth in patient-derived cell lines. KMT5B homozygous knockout mice were smaller in size than their wild-type littermates but did not have significantly smaller brains, suggesting relative macrocephaly, also noted as a prominent clinical feature. RNA sequencing of patient lymphoblasts and haploinsufficient mouse brains identified differentially expressed pathways associated with nervous system development and function including axon guidance signaling. Overall, we identified additional pathogenic variants and clinical features in -related neurodevelopmental disorder and provide insights into the molecular mechanisms of the disorder using multiple model systems.
Topics: Animals; Humans; Mice; Haploinsufficiency; Megalencephaly; Methyltransferases; Mice, Knockout; Neurodevelopmental Disorders; Phenotype
PubMed: 36897941
DOI: 10.1126/sciadv.ade1463