The Aicardi-Goutières syndrome (familial, early onset encephalopathy with calcifications of the basal ganglia and chronic cerebrospinal fluid lymphocytosis)

Macrocephaly and Finger Changes: A Narrative 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.

TREX1 is required for microglial cholesterol homeostasis and oligodendrocyte terminal differentiation in human neural assembloids

Three Prime Repair Exonuclease 1 (TREX1) gene mutations have been associated with Aicardi-Goutières Syndrome (AGS) - a rare, severe pediatric autoimmune disorder that primarily affects the brain and has a poorly understood etiology. Microglia are brain-resident macrophages indispensable for brain development and implicated in multiple neuroinflammatory diseases. However, the role of TREX1 - a DNase that cleaves cytosolic nucleic acids, preventing viral- and autoimmune-related inflammatory responses - in microglia biology remains to be elucidated. Here, we leverage a model of human embryonic stem cell (hESC)-derived engineered microglia-like cells, bulk, and single-cell transcriptomics, optical and transmission electron microscopy, and three-month-old assembloids composed of microglia and oligodendrocyte-containing organoids to interrogate TREX1 functions in human microglia. Our analyses suggest that TREX1 influences cholesterol metabolism, leading to an active microglial morphology with increased phagocytosis in the absence of TREX1. Notably, regulating cholesterol metabolism with an HMG-CoA reductase inhibitor, FDA-approved atorvastatin, rescues these microglial phenotypes. Functionally, TREX1 in microglia is necessary for the transition from gliogenic intermediate progenitors known as pre-oligodendrocyte precursor cells (pre-OPCs) to precursors of the oligodendrocyte lineage known as OPCs, impairing oligodendrogenesis in favor of astrogliogenesis in human assembloids. Together, these results suggest routes for therapeutic intervention in pathologies such as AGS based on microglia-specific molecular and cellular mechanisms.

Leukodystrophy Imaging: Insights for Diagnostic Dilemmas

Leukodystrophies, a group of rare demyelinating disorders, mainly affect the CNS. Clinical presentation of different types of leukodystrophies can be nonspecific, and thus, imaging techniques like MRI can be used for a more definitive diagnosis. These diseases are characterized as cerebral lesions with characteristic demyelinating patterns which can be used as differentiating tools. In this review, we talk about these MRI study findings for each leukodystrophy, associated genetics, blood work that can help in differentiation, emerging diagnostics, and a follow-up imaging strategy. The leukodystrophies discussed in this paper include X-linked adrenoleukodystrophy, metachromatic leukodystrophy, Krabbe's disease, Pelizaeus-Merzbacher disease, Alexander's disease, Canavan disease, and Aicardi-Goutières Syndrome.

Biochemical functions and structure of Caenorhabditis elegans ZK177.8 protein: Aicardi-Goutières syndrome SAMHD1 dNTPase ortholog

Mutations in sterile alpha motif domain and histidine-aspartate domain-containing protein 1 (SAMHD1) are found in a neurodevelopmental disorder, Aicardi-Goutières syndrome, and cancers, and SAMHD1, which is a deoxynucleoside triphosphate (dNTP) triphosphorylase, was identified as a myeloid-specific HIV-1 restriction factor. Here, we characterized the enzymology and structure of an SAMHD1 ortholog of Caenorhabditis elegans, ZK177.8, which also reportedly induces developmental defects upon gene knockdown. We found ZK177.8 protein is a dNTPase allosterically regulated by dGTP. The active site of ZK177.8 recognizes both 2' OH and triphosphate moieties of dNTPs but not base moiety. The dGTP activator induces the formation of the enzymatically active ZK177.8 tetramers, and ZK177.8 protein lowers cellular dNTP levels in a human monocytic cell line. Finally, ZK177.8 tetramers display very similar X-ray crystal structure with human and mouse SAMHD1s except that its lack of the canonical sterile alpha motif domain. This striking conservation in structure, function, and allosteric regulatory mechanism for the hydrolysis of the DNA building blocks supports their host developmental roles.

The neurovascular unit in leukodystrophies: towards solving the puzzle

The neurovascular unit (NVU) is a highly organized multicellular system localized in the brain, formed by neuronal, glial (astrocytes, oligodendrocytes, and microglia) and vascular (endothelial cells and pericytes) cells. The blood-brain barrier, a complex and dynamic endothelial cell barrier in the brain microvasculature that separates the blood from the brain parenchyma, is a component of the NVU. In a variety of neurological disorders, including Alzheimer's disease, multiple sclerosis, and stroke, dysfunctions of the NVU occurs. There is, however, a lack of knowledge regarding the NVU function in leukodystrophies, which are rare monogenic disorders that primarily affect the white matter. Since leukodystrophies are rare diseases, human brain tissue availability is scarce and representative animal models that significantly recapitulate the disease are difficult to develop. The introduction of human induced pluripotent stem cells (hiPSC) now makes it possible to surpass these limitations while maintaining the ability to work in a biologically relevant human context and safeguarding the genetic background of the patient. This review aims to provide further insights into the NVU functioning in leukodystrophies, with a special focus on iPSC-derived models that can be used to dissect neurovascular pathophysiology in these diseases.

Astrocytes, an active player in Aicardi-Goutières syndrome

Aicardi-Goutières syndrome (AGS) is an early-onset, autoimmune and genetically heterogeneous disorder with severe neurologic injury. Molecular studies have established that autosomal recessive mutations in one of the following genes are causative: TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR1 and IFIH1/MDA5. The phenotypic presentation and pathophysiology of AGS is associated with over-production of the cytokine Interferon-alpha (IFN-α) and its downstream signaling, characterized as type I interferonopathy. Astrocytes are one of the major source of IFN in the central nervous system (CNS) and it is proposed that they could be key players in AGS pathology. Astrocytes are the most ubiquitous glial cell in the CNS and perform a number of crucial and complex functions ranging from formation of blood-brain barrier, maintaining ionic homeostasis, metabolic support to synapse formation and elimination in healthy CNS. Involvement of astrocytic dysfunction in neurological diseases-Alexander's disease, Epilepsy, Alzheimer's and amyotrophic lateral sclerosis (ALS)-has been well-established. It is now known that compromised astrocytic function can contribute to CNS abnormalities and severe neurodegeneration, nevertheless, its contribution in AGS is unclear. The current review discusses known molecular and cellular pathways for AGS mutations and how it stimulates IFN-α signaling. We shed light on how astrocytes might be key players in the phenotypic presentations of AGS and emphasize the cell-autonomous and non-cell-autonomous role of astrocytes. Understanding the contribution of astrocytes will help reveal mechanisms underlying interferonopathy and develop targeted astrocyte specific therapeutic treatments in AGS.

JAK Inhibitors in Rheumatology: Implications for Paediatric Syndromes?

PURPOSE OF REVIEW

Given the recent increase in the profile and use of Janus kinase inhibitors (JAKinibs) in adult patients with rheumatic diseases, we aimed to review the current evidence accruing for use in paediatric rheumatology patients.

RECENT FINDINGS

Significant advances have been made in the management of rheumatic diseases in the past two decades. The introduction of biologic agents in both adults and children has provided significant improvements to patient outcomes and led to better quality of life. Moreover, responses to similar agents allude to common effector pathways operating across juvenile and adult synovitis especially. However, inefficacy and intolerance of these agents leads to a subset of children with limited treatment options. Since 2012, Janus kinase (JAK) inhibitors (JAKinibs), a novel group of oral small molecule inhibitors, have demonstrated their efficacy in several forms of adult inflammatory arthritis, such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA). There are hopes that these successes will be transferable to the paediatric population. In the following review, we discuss the development and progress of JAKinibs in this regard.

Leukodystrophies

PURPOSE OF REVIEW

The leukodystrophies, typically considered incurable neurodegenerative disorders, are often diagnosed after irreversible central and peripheral nervous system injury has occurred. Early recognition of these disorders is imperative to enable potential therapeutic interventions. This article provides a summary of the symptoms of and diagnostic evaluation for leukodystrophies, along with the currently available therapies and recent advances in management.

RECENT FINDINGS

The leukodystrophies are a rapidly expanding field because of advances in neuroimaging and genetics; however, recognition of the clinical and biochemical features of a leukodystrophy is essential to accurately interpret an abnormal MRI or genetic result. Moreover, the initial symptoms of leukodystrophies may mimic other common pediatric disorders, leading to a delay in the recognition of a degenerative disorder.

SUMMARY

This article will aid the clinician in recognizing the clinical features of leukodystrophies and providing accurate diagnosis and management.

Aicardi-Goutières Syndrome: Brief Case Report

The case of a term newborn diagnosed with Aicardi-Goutières syndrome, a rare encephalopathy in our environment, with Mendelian inheritance pattern, characterized by a set of nonspecific neurological symptoms associated with typical findings of intracerebral calcifications. The case is presented with diagnostic imaging, in addition to elevated levels of interferon alpha and cerebrospinal fluid lymphocytosis.

Monogenic Lupus

PURPOSE OF REVIEW

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease known for its clinical heterogeneity. Over time, new insights into the complex genetic origin of SLE have started to explain some of this clinical variability. These findings, reviewed here, have also yielded important understanding in the immune mechanisms behind SLE pathogenesis.

RECENT FINDINGS

Several new monogenic disorders with lupus-like phenotype have been described. These can be organized into physiologic pathways that parallel mechanisms of disease in SLE. Examples include genes important for DNA damage repair (e.g., TREX1), nucleic acid sensing and type I interferon overproduction (e.g., STING, TREX1), apoptosis (FASLG), tolerance (PRKCD), and clearance of self-antigen (DNASE1L3). Further study of monogenic lupus may lead to better genotype/phenotype correlations in SLE. Eventually, the ability to understand individual patients according to their genetic profile may allow the development of more targeted and personalized approaches to therapy.

Aicardi-Goutières syndrome: unusual neuro-radiological manifestations

Aicardi-Goutières syndrome (AGS) is one of the expanding group of inherited congenital infection like syndromes. Here, we describe the detailed clinical and imaging findings of two sibs with AGS. Each shows scattered periventricular intracranial calcifications, severe global delay, seizures, microcephaly and spasticity. Interestingly, chilblains were observed in the two sisters as well as their parents and a paternal uncle. The brain MRI of the older sister showed marked ventricular dilatation as a result of unusual associated porencephalic cysts. Unexpectedly, unilateral cerebellar hypoplasia was also noted. In comparison, her younger sister displayed the classic atrophic changes and white matter loss of AGS. The diagnosis of AGS was confirmed by sequence analysis, which identified a previously reported homozygous RNASEH2B mutation, c.554 T > G (p.V185G). Parents were heterozygous for the same mutation. Further molecular analysis excluded mutations in potentially related manifestations of COL4A1 gene. This is the first report of chilblains associated with heterozygous RNASEH2B mutation. Further, the brain imaging findings appear particularly interesting, which until now has not been reported in any AGS patient. We discuss the possible reasons for this unusual presentation.

Aicardi-Goutières syndrome and the type I interferonopathies

Dissection of the genetic basis of Aicardi-Goutières syndrome has highlighted a fundamental link between nucleic acid metabolism, innate immune sensors and type I interferon induction. This had led to the concept of the human interferonopathies as a broader set of Mendelian disorders in which a constitutive upregulation of type I interferon activity directly relates to disease pathology. Here, we discuss the molecular and cellular basis of the interferonopathies, their categorization, future treatment strategies and the insights they provide into normal physiology.

Type I interferonopathies--an expanding disease spectrum of immunodysregulation

Type I interferons (IFNs) play a central role in the immune defense against viral infections. Type I IFN signaling is activated by pattern recognition receptors upon sensing of viral nucleic acids and induces antiviral programs through modulation of innate and adaptive immune responses. Type I interferonopathies comprise a heterogenous group of genetically determined diseases that are characterized by inappropriate activation of type I IFN. While their phenotypic spectrum is broad, ranging from severe neurological impairment to mild cutaneous disease, systemic autoinflammation, and autoimmunity are commonly shared signs of type I interferonopathies. Although the mechanisms underlying various disease phenotypes associated with inappropriate type I IFN activation have yet to be fully elucidated, our current understanding of the molecular pathogenesis of type I interferonopathies has provided a set of candidate molecules that can be interrogated in search of targeted therapies.

Characterization of human disease phenotypes associated with mutations in TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR, and IFIH1

Aicardi-Goutières syndrome is an inflammatory disease occurring due to mutations in any of TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR or IFIH1. We report on 374 patients from 299 families with mutations in these seven genes. Most patients conformed to one of two fairly stereotyped clinical profiles; either exhibiting an in utero disease-onset (74 patients; 22.8% of all patients where data were available), or a post-natal presentation, usually within the first year of life (223 patients; 68.6%), characterized by a sub-acute encephalopathy and a loss of previously acquired skills. Other clinically distinct phenotypes were also observed; particularly, bilateral striatal necrosis (13 patients; 3.6%) and non-syndromic spastic paraparesis (12 patients; 3.4%). We recorded 69 deaths (19.3% of patients with follow-up data). Of 285 patients for whom data were available, 210 (73.7%) were profoundly disabled, with no useful motor, speech and intellectual function. Chilblains, glaucoma, hypothyroidism, cardiomyopathy, intracerebral vasculitis, peripheral neuropathy, bowel inflammation and systemic lupus erythematosus were seen frequently enough to be confirmed as real associations with the Aicardi-Goutieres syndrome phenotype. We observed a robust relationship between mutations in all seven genes with increased type I interferon activity in cerebrospinal fluid and serum, and the increased expression of interferon-stimulated gene transcripts in peripheral blood. We recorded a positive correlation between the level of cerebrospinal fluid interferon activity assayed within one year of disease presentation and the degree of subsequent disability. Interferon-stimulated gene transcripts remained high in most patients, indicating an ongoing disease process. On the basis of substantial morbidity and mortality, our data highlight the urgent need to define coherent treatment strategies for the phenotypes associated with mutations in the Aicardi-Goutières syndrome-related genes. Our findings also make it clear that a window of therapeutic opportunity exists relevant to the majority of affected patients and indicate that the assessment of type I interferon activity might serve as a useful biomarker in future clinical trials.

Therapies in Aicardi-Goutières syndrome

Aicardi-Goutières syndrome (AGS) is a genetically determined disorder, affecting most particularly the brain and the skin, characterized by the inappropriate induction of a type I interferon-mediated immune response. In most, but not all, cases the condition is severe, with a high associated morbidity and mortality. A number of important recent advances have helped to elucidate the biology of the AGS-related proteins, thus providing considerable insight into disease pathology. In this study, we outline the clinical phenotype of AGS, paying particular attention to factors relevant to therapeutic intervention. We then discuss the pathogenesis of AGS from a molecular and cell biology perspective. Finally, we suggest possible treatment strategies in light of these emerging insights.

Aicardi-Goutières syndrome: a model disease for systemic autoimmunity

Systemic autoimmunity is a complex disease process that results from a loss of immunological tolerance characterized by the inability of the immune system to discriminate self from non-self. In patients with the prototypic autoimmune disease systemic lupus erythematosus (SLE), formation of autoantibodies targeting ubiquitous nuclear antigens and subsequent deposition of immune complexes in the vascular bed induces inflammatory tissue injury that can affect virtually any organ system. Given the extraordinary genetic and phenotypic heterogeneity of SLE, one approach to the genetic dissection of complex SLE is to study monogenic diseases, for which a single gene defect is responsible. Considerable success has been achieved from the analysis of the rare monogenic disorder Aicardi-Goutières syndrome (AGS), an inflammatory encephalopathy that clinically resembles in-utero-acquired viral infection and that also shares features with SLE. Progress in understanding the cellular and molecular functions of the AGS causing genes has revealed novel pathways of the metabolism of intracellular nucleic acids, the major targets of the autoimmune attack in patients with SLE. Induction of autoimmunity initiated by immune recognition of endogenous nucleic acids originating from processes such as DNA replication/repair or endogenous retro-elements represents novel paradigms of SLE pathogenesis. These findings illustrate how investigating rare monogenic diseases can also fuel discoveries that advance our understanding of complex disease. This will not only aid the development of improved tools for SLE diagnosis and disease classification, but also the development of novel targeted therapeutic approaches.

Therapies in Aicardi-Goutières syndrome

Aicardi-Goutières syndrome (AGS) is a genetically determined disorder, affecting most particularly the brain and the skin, characterized by the inappropriate induction of a type I interferon-mediated immune response. In most, but not all, cases the condition is severe, with a high associated morbidity and mortality. A number of important recent advances have helped to elucidate the biology of the AGS-related proteins, thus providing considerable insight into disease pathology. In this study, we outline the clinical phenotype of AGS, paying particular attention to factors relevant to therapeutic intervention. We then discuss the pathogenesis of AGS from a molecular and cell biology perspective. Finally, we suggest possible treatment strategies in light of these emerging insights.

Assessment of interferon-related biomarkers in Aicardi-Goutières syndrome associated with mutations in TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, and ADAR: a case-control study

BACKGROUND

Aicardi-Goutières syndrome (AGS) is an inflammatory disorder caused by mutations in any of six genes (TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, and ADAR). The disease is severe and effective treatments are urgently needed. We investigated the status of interferon-related biomarkers in patients with AGS with a view to future use in diagnosis and clinical trials.

METHODS

In this case-control study, samples were collected prospectively from patients with mutation-proven AGS. The expression of six interferon-stimulated genes (ISGs) was measured by quantitative PCR, and the median fold change, when compared with the median of healthy controls, was used to create an interferon score for each patient. Scores higher than the mean of controls plus two SD (>2·466) were designated as positive. Additionally, we collated historical data for interferon activity, measured with a viral cytopathic assay, in CSF and serum from mutation-positive patients with AGS. We also undertook neutralisation assays of interferon activity in serum, and looked for the presence of autoantibodies against a panel of interferon proteins.

FINDINGS

74 (90%) of 82 patients had a positive interferon score (median 12·90, IQR 6·14-20·41) compared with two (7%) of 29 controls (median 0·93, IQR 0·57-1·30). Of the eight patients with a negative interferon score, seven had mutations in RNASEH2B (seven [27%] of all 26 patients with mutations in this gene). Repeat sampling in 16 patients was consistent for the presence or absence of an interferon signature on 39 of 41 occasions. Interferon activity (tested in 147 patients) was negatively correlated with age (CSF, r=-0·604; serum, r=-0·289), and was higher in CSF than in serum in 104 of 136 paired samples. Neutralisation assays suggested that measurable antiviral activity was related to interferon α production. We did not record significantly increased concentrations of autoantibodies to interferon subtypes in patients with AGS, or an association between the presence of autoantibodies and interferon score or serum interferon activity.

INTERPRETATION

AGS is consistently associated with an interferon signature, which is apparently sustained over time and can thus be used to differentiate patients with AGS from controls. If future studies show that interferon status is a reactive biomarker, the measurement of an interferon score might prove useful in the assessment of treatment efficacy in clinical trials.

FUNDING

European Union's Seventh Framework Programme; European Research Council.

Aicardi-Goutières syndrome

Aicardi-Goutières syndrome (AGS) is a genetically determined encephalopathy demonstrating phenotypic overlap both with the sequelae of congenital infection and with systemic lupus erythematosus (SLE). Recent molecular advances have revealed that AGS can be caused by mutations in any one of five genes, most commonly on a recessive basis but occasionally as a dominant trait. Like AGS, SLE is associated with a perturbation of type I interferon metabolism. Interestingly then, heterozygous mutations in the AGS1 gene TREX1, and the AGS5 gene SAMHD1, underlie a cutaneous subtype of SLE called familial chilblain lupus, and mutations in TREX1 represent the single most common cause of monogenic SLE identified to date. Evidence is emerging to show that the nucleases defective in AGS are involved in removing endogenously produced nucleic acid species, and that a failure of this removal results in activation of the immune system. This hypothesis explains the phenotypic overlap of AGS with congenital infection and some aspects of SLE, where an equivalent type I interferon-mediated innate immune response is triggered by viral and self nucleic acids respectively. These studies beg urgent questions about the development and use of immunosuppressive therapies in AGS and related phenotypes.

Aicardi-Goutières syndrome with emphasis on sonographic features in infancy

BACKGROUND

Aicardi-Goutières syndrome (AGS) is a severe familial, mostly autosomal recessive encephalopathy, first described in 1984. The clinical picture and genetic abnormalities are heterogeneous. US findings in AGS have thus far not been systematically described.

OBJECTIVE

The purpose of this study was to analyse sonographic features in AGS and to compare them to CT/MRI.

MATERIALS AND METHODS

Four male infants with AGS, two brothers, underwent imaging between the ages of 4 weeks and 6 months.

RESULTS

Sonographically isolated mineralization of lenticulostriate vessels, dilatation of the lateral ventricles, subependymal cysts, and diffuse and focal hyperechogenicity of the periventricular white matter and basal ganglia, respectively, were the abnormal findings, that may be present even before the development of major neurological symptoms.

CONCLUSION

Early cranial US is able to visualize the whole spectrum of cerebral anomalies in AGS: calcifying microangiopathy, white matter disease and unusual subependymal cysts. The imaging pattern is similar to that of congenital viral infection of the central nervous system, which may mislead the genetic counseling.

The Aicardi-Goutières syndrome. Molecular and clinical features of RNAse deficiency and microRNA overload

Intracellular RNAses are involved in various functions, including microRNA maturation and turnover. Mutations occurring in genes encoding RNAses cause Aicardi-Goutiéres syndrome (AGS). AGS mutations silence RNAse activity, thus inducing accumulation of endogenous RNAs, mainly consisting of short RNAs and microRNAs. Overload of intracellular RNA triggers Toll like receptor-dependent interferon-alpha production in the brain, which in turn activates neurotoxic lymphocytes and inhibits angiogenesis thus inducing the typical clinical phenotype of AGS. However, these pathogenic mechanisms are attenuated after three years of age by the endogenous production of DNAJP58IPK and Cystatin F, which arrest AGS progression. Because RNAses are involved in microRNA turnover, we evaluated the expression of 957 microRNAs in lymphocytes from AGS patients and control patients. Our results indicate that microRNA overload occurs in AGS patients. This upregulation inhibits microRNA turnover impeding the synthesis of the novel microRNAs required for the differentiation and myelination of the brain during the initial period of postnatal life. These pathogenic mechanisms result in AGS, a neurological syndrome characterized by irritability, mild hyperpyrexia, pyramidal and extrapyramidal signs, and spastic-dystonic tetraplegia. Typical cerebrospinal fluid alterations include lymphocytosis and elevated interferon-alpha levels. Brain imaging demonstrates cerebral calcifications, white matter abnormalities, and progressive cerebral atrophy.Thus, evidence exists that mutations silencing intracellular RNases affect microRNA turnover resulting in the severe clinical consequences in the brain characterizing the clinical feature of AGS.

Cerebral arterial stenoses and stroke: novel features of Aicardi-Goutières syndrome caused by the Arg164X mutation in SAMHD1 are associated with altered cytokine expression

Aicardi-Goutières syndrome (AGS) is a rare inborn multisystemic disease, resembling intrauterine viral infection and resulting in psychomotor retardation, spasticity and chilblain-like skin lesions. Diagnostic criteria include intracerebral calcifications and elevated interferon-alpha and pterin levels in cerebrospinal fluid (CSF). We report on four adult siblings with unknown neurodegenerative disease presenting with cerebrovascular stenoses, stroke and glaucoma in childhood, two of whom died at the age of 40 and 29 years. Genome-wide homozygosity mapping identified 170 candidate genes embedded in a common haplotype of 8Mb on chromosome 20q11-13. Next generation sequencing of the entire region identified the c.490C>T (p.Arg164X) mutation in SAMHD1, a gene most recently described in AGS, on both alleles in all affected siblings. Clinical diagnosis of AGS was then confirmed by demonstrating intracerebral calcifications on cranial computed tomography in all siblings and elevated pterin levels in CSF in three of them. In patient fibroblasts, lack of SAMHD1 protein expression was associated with increased basal expression of IL8, while stimulated expression of IFNB1 was reduced. We conclude that cerebrovascular stenoses and stroke associated with the Arg164X mutation in SAMHD1 extend the phenotypic spectrum of AGS. The observed vascular changes most likely reflect a vasculitis caused by dysregulated inflammatory stress response. © 2010 Wiley-Liss, Inc.

Identification of a novel genetic locus on chromosome 8p21.1-q11.23 for idiopathic basal ganglia calcification

Idiopathic basal ganglia calcification (IBGC) is a neurodegenerative disorder that is characterized by basal ganglia and extrabasal ganglia calcification, and usually inherited in an autosomal dominant pattern. To date, two genetic loci for IBGC were identified on chromosomes 14q and 2q, but further genetic heterogeneity clearly exists. In this study, a large Chinese family with autosomal dominant IBGC was characterized. Linkage analysis excluded the 14q13 and 2q37 loci. The large family was then characterized by genome-wide linkage analysis to identify a novel genetic locus for IBGC. Significant linkage was identified with markers on chromosome 8p21.1-q11.23 with a maximum LOD score of 4.10. Fine mapping defined the new genetic locus within a 25 Mb region between markers D8S1809 and D8S1833. Future studies of the candidate genes at the 8p21.1-q11.23 locus may lead to identification of a disease-causing gene with IBGC.

Aicardi-Goutières syndrome: cutaneous, laboratory, and radiologic findings: a case report

Aicardi-Goutières syndrome is a primarily autosomal recessive disorder characterized by congenital encephalopathy, basal ganglia calcifications, elevated interferon-alpha in blood and cerebral spinal fluid, and negative studies for intrauterine infections that can mimic the syndrome. Cutaneous manifestations include pernio, photosensitivity, and cutaneous vasculitis. We present a case of Aicardi-Goutières syndrome to increase awareness of the disorder and its possible relation to systemic lupus erythematosus.

Agenesis of the corpus callosum in fetuses with mild ventriculomegaly: role of MR imaging

PURPOSE

We evaluated the role of magnetic resonance (MR) imaging in the diagnosis of corpus callosum agenesis - isolated or associated with other anomalies - in fetuses with mild cerebral ventriculomegaly, as depicted at prenatal sonography.

MATERIAL AND METHODS

Between January 2005 and March 2007, 33 fetuses with a mean gestational age of 28.9 weeks (range 17-37) and mild ventriculomegaly diagnosed at prenatal sonography were included in this prospective study. All fetuses underwent MR imaging according to the following protocol: half-Fourier T2-weighted images along the three orthogonal plane according to the longitudinal axis of the mother, and subsequently three orthogonal planes were acquired according to the fetal brain. Quantitative image analysis included the size of the transverse diameter of the lateral ventricles, in the axial plane, and the thickness of the adjacent cerebral cortex. Qualitative image analysis included morphology of the lateral ventricles (normal, parallel pattern colpocephaly), signal intensity changes of the fetal brain, interruption of the germinative matrix, agenesis of the corpus callosum (complete/partial) and associated malformations. Postnatal physical examination and diagnostic imaging, as well as surgery, were the standard of diagnosis.

RESULTS

Mean axial diameter of the lateral ventricle was 11.6 mm (range 10-15 mm), and mean thickness of the adjacent cerebral cortex was 2.1 mm (range 1.8-3 mm); 23/33 fetuses (70%) showed normal morphology of the lateral ventricles, and 8/33 (24%) showed abnormal morphology (parallel pattern, colpocephaly). The entire corpus callosum was visualised in 20/33 fetuses (60%). In 8/33 fetuses (25%), partial agenesis was diagnosed, whereas in 5/33 (15%), there was hypogenesis. In 6/13 fetuses (46%), isolated corpus callosum agenesis was detected, and two cases of hypogenesis of the corpus callosum were misinterpreted - overestimated in one case and underestimated in another.

CONCLUSIONS

MR imaging may prove to be a useful second-line imaging modality in the prenatal diagnosis of corpus callosum agenesis in fetuses with mild ventriculomegaly.

Aicardi-Goutières syndrome presenting with haematemesis in infancy

Aicardi-Goutières syndrome is a genetic childhood encephalopathy characterized by basal ganglia calcification, chronic cerebrospinal lymphocytosis and elevated cerebrospinal fluid interferon-alpha, mimicking acquired congenital viral infections. As more is discovered about the pathogenesis of Aicardi-Goutières, it is becoming evident that a dysfunction of the immune system is likely to be responsible for the disease phenotype. We describe a previously healthy 2-month-old female infant who presented with haematemesis and seizures and was subsequently diagnosed with Aicardi-Goutières syndrome. To our knowledge, this is the first documented case of Aicardi-Goutières syndrome presenting with haematemesis. The gastrointestinal tract is an area of high cell loss, revealing early signs of systemic inflammation and we postulate that a systemic proinflammatory milieu occurs in Aicardi-Goutières syndrome.

CONCLUSION

Aicardi-Goutières syndrome can present with haematemesis, adding to the growing evidence that the Aicardi-Goutières syndrome spectrum encompasses an immune-mediated multisystem involvement. Gastrointestinal inflammation should also be considered in these patients and treated appropriately.

Recessive developmental delay, small stature, microcephaly and brain calcifications with locus on chromosome 2

Two interrelated Omani families are described with eight children manifesting a genetic disorder with widespread brain calcifications. Brain imaging showed extensive scattered calcifications of basal ganglia and cortex, suggesting possible Aicardi-Goutieres syndrome (AGS) or Coats' Plus syndrome. However, the clinical features in the present families diverge substantially from these two conditions. Growth delay, mild developmental delay, and poor school performance were present in all affected individuals, but progressive deterioration of neurological function was not apparent, nor were there significant cortical whitematter disease or retinopathy. Genome-wide linkage and fine-mapping analyses of the extended family members and affected individuals indicate a genetic locus for this disorder on Chromosome 2 with a LOD score of 6.17. The Chromosome 2 locus is novel and the clinical presentation displays features distinguishing the condition from either Coats' or AGS, making this a new variant or possibly a new disorder of inherited brain calcification.

RNaseH2 mutants that cause Aicardi-Goutieres syndrome are active nucleases

Mutations in the genes encoding the RNaseH2 and TREX1 nucleases have been identified in patients with Aicardi-Goutieres syndrome (AGS). To determine if the AGS RNaseH2 mutations result in the loss of nuclease activity, the human wild-type RNaseH2 and four mutant complexes that constitute the majority of mutations identified in AGS patients have been prepared and tested for ribonuclease H activity. The heterotrimeric structures of the mutant RNaseH2 complexes are intact. Furthermore, the ribonuclease H activities of the mutant complexes are indistinguishable from the wild-type enzyme with the exception of the RNaseH2 subunit A (Gly37Ser) mutant, which exhibits some evidence of altered nuclease specificity. These data indicate that the mechanism of RNaseH2 dysfunction in AGS cannot be simply explained by loss of ribonuclease H activity and points to a more complex mechanism perhaps mediated through altered interactions with as yet identified nucleic acids or protein partners.

Aicardi-Goutières syndrome (AGS)

In 1984, Jean Aicardi and Françoise Goutières described 8 children showing both severe brain atrophy and chronic cerebrospinal fluid lymphocytosis, with basal ganglia calcification in at least one member of each affected family. The course was rapid to death or a vegetative outcome. Aicardi and Goutières correctly predicted that the disorder would be genetic, but emphasised that "some features, especially the pleocytosis, may erroneously suggest an inflammatory condition". The increased interferon-alpha in affected children (Pierre Lebon, Paris) mimicked congenital viral infection, but the associated chilblains (pernio) pointed to lupus erythematosus and an autoimmune mechanism. Genetic research led by Yanick Crow has clarified these puzzling relationships in Aicardi-Goutières syndrome, a syndrome that now includes conditions previously known as microcephaly-intracranial calcification syndrome, pseudo-TORCH and Cree encephalitis. At the time of writing, Crow's team has discovered that over 80% of families with Aicardi-Goutières syndrome have mutations in one of four nuclease genes, the exonuclease TREX1 and the genes for all three subunits of the ribonuclease H2 enzyme complex. Aicardi-Goutières syndrome is both genetically and phenotypically heterogeneous, with a range of severity from life-threatening perinatal illness to mild late infancy onset. All infants of whatever genotype have increased interferon-alpha in the first year of life and this appears to be the final common pathway that links Aicardi-Goutières syndrome, congenital virus infection and systemic lupus erythematosus.

Aicardi-Goutières syndrome: an important Mendelian mimic of congenital infection

Aicardi-Goutières syndrome (AGS) is a rare, genetically determined encephalopathy whose importance from a clinical viewpoint is magnified because of the risk of misdiagnosis as the sequelae of congenital infection. Recent molecular advances have shown that AGS can be caused by mutations in any one of at least five genes (four of which have so far been identified), most commonly on a recessive basis but occasionally as a dominant trait. Additionally, a recent genotype-phenotype correlation has shown that two clinical presentations can be delineated; an early onset neonatal form highly reminiscent of congenital infection seen particularly with TREX1 mutations, and a later-onset presentation, sometimes occurring after several months of normal development and occasionally associated with remarkably preserved neurological function, most frequently due to RNASEH2B mutations. Evidence is emerging to show that the nucleases defective in AGS are involved in removing endogenous nucleic acid species produced during normal cellular processing, and that a failure of this removal results in inappropriate activation of the innate immune system. This hypothesis explains the phenotypic overlap of AGS with congenital infection and some aspects of systemic lupus erythematosus, where a similar interferon alpha-mediated innate immune response is triggered by viral and host nucleic acids respectively.

Cutaneous histopathological findings of Aicardi-Goutières syndrome, overlap with chilblain lupus

We report a 2-year-old girl with developmental delay who, from the age of 1 year, developed perniotic lesions of the hands and feet initially diagnosed as chilblain lupus. Histological examination showed features of epidermal necrosis with intraepidermal bulla formation, interface dermatitis, lymphocytic vasculitis with fibrinoid necrosis and thrombi formation, both superficial and deep dermal lymphocytic infiltrate, lymphocytic eccrine hidradenitis and absence of marked dermal edema. Subsequent investigations suggested a clinical diagnosis of Aicardi-Goutières syndrome (AGS), a rare genetic leukoencephalopathy. Recently, both AGS and familial chilblain lupus, an autosomal dominant form of systemic lupus erythematosus (SLE), have been shown to be allelic thus suggesting a common pathogenic basis. In addition, a phenotypic overlap is apparent between SLE and AGS. To our knowledge, this is the first comprehensive dermatopathological report of the cutaneous lesions seen in AGS, and our paper highlights the importance of considering AGS in the differential diagnosis of perniosis and chilblain lupus.

Clinical and molecular phenotype of Aicardi-Goutieres syndrome

Aicardi-Goutieres syndrome (AGS) is a genetic encephalopathy whose clinical features mimic those of acquired in utero viral infection. AGS exhibits locus heterogeneity, with mutations identified in genes encoding the 3'-->5' exonuclease TREX1 and the three subunits of the RNASEH2 endonuclease complex. To define the molecular spectrum of AGS, we performed mutation screening in patients, from 127 pedigrees, with a clinical diagnosis of the disease. Biallelic mutations in TREX1, RNASEH2A, RNASEH2B, and RNASEH2C were observed in 31, 3, 47, and 18 families, respectively. In five families, we identified an RNASEH2A or RNASEH2B mutation on one allele only. In one child, the disease occurred because of a de novo heterozygous TREX1 mutation. In 22 families, no mutations were found. Null mutations were common in TREX1, although a specific missense mutation was observed frequently in patients from northern Europe. Almost all mutations in RNASEH2A, RNASEH2B, and RNASEH2C were missense. We identified an RNASEH2C founder mutation in 13 Pakistani families. We also collected clinical data from 123 mutation-positive patients. Two clinical presentations could be delineated: an early-onset neonatal form, highly reminiscent of congenital infection seen particularly with TREX1 mutations, and a later-onset presentation, sometimes occurring after several months of normal development and occasionally associated with remarkably preserved neurological function, most frequently due to RNASEH2B mutations. Mortality was correlated with genotype; 34.3% of patients with TREX1, RNASEH2A, and RNASEH2C mutations versus 8.0% RNASEH2B mutation-positive patients were known to have died (P=.001). Our analysis defines the phenotypic spectrum of AGS and suggests a coherent mutation-screening strategy in this heterogeneous disorder. Additionally, our data indicate that at least one further AGS-causing gene remains to be identified.

Heterozygous mutations in TREX1 cause familial chilblain lupus and dominant Aicardi-Goutieres syndrome

TREX1 constitutes the major 3'-->5' DNA exonuclease activity measured in mammalian cells. Recently, biallelic mutations in TREX1 have been shown to cause Aicardi-Goutieres syndrome at the AGS1 locus. Interestingly, Aicardi-Goutieres syndrome shows overlap with systemic lupus erythematosus at both clinical and pathological levels. Here, we report a heterozygous TREX1 mutation causing familial chilblain lupus. Additionally, we describe a de novo heterozygous mutation, affecting a critical catalytic residue in TREX1, that results in typical Aicardi-Goutieres syndrome.

Regression of white matter hypodensities with age in Aicardi-Goutierés syndrome: a case report

BACKGROUND

Aicardi-Goutierés syndrome (AGS) is a severe and progressive familial encephalopathy that is characterized by acquired microcephaly, intracranial calcification, white matter lesions, and chronic lymphocytosis with elevated levels of interferon-alpha in the cerebrospinal fluid. Although the degree of calcification and the severity of brain atrophy are variable, typically, the brain lesions appear to progress on successive examinations.

CASE REPORT

We report a 7-year-old male patient who showed relative regression of white matter lesions with nonprogression of basal ganglia calcification and atrophy on follow-up magnetic resonance imaging and computed tomography scans.

RESULTS

Magnetic resonance spectroscopy findings were normal. This, to our knowledge, is the first case report, which describes relative regression of the white matter changes in AGS.

Familial chilblain lupus, a monogenic form of cutaneous lupus erythematosus, maps to chromosome 3p

Systemic lupus erythematosus is a prototypic autoimmune disease. Apart from rare monogenic deficiencies of complement factors, where lupuslike disease may occur in association with other autoimmune diseases or high susceptibility to bacterial infections, its etiology is multifactorial in nature. Cutaneous findings are a hallmark of the disease and manifest either alone or in association with internal-organ disease. We describe a novel genodermatosis characterized by painful bluish-red inflammatory papular or nodular lesions in acral locations such as fingers, toes, nose, cheeks, and ears. The lesions sometimes appear plaquelike and tend to ulcerate. Manifestation usually begins in early childhood and is precipitated by cold and wet exposure. Apart from arthralgias, there is no evidence for internal-organ disease or an increased susceptibility to infection. Histological findings include a deep inflammatory infiltrate with perivascular distribution and granular deposits of immunoglobulins and complement along the basement membrane. Some affected individuals show antinuclear antibodies or immune complex formation, whereas cryoglobulins or cold agglutinins are absent. Thus, the findings are consistent with chilblain lupus, a rare form of cutaneous lupus erythematosus. Investigation of a large German kindred with 18 affected members suggests a highly penetrant trait with autosomal dominant inheritance. By single-nucleotide-polymorphism-based genomewide linkage analysis, the locus was mapped to chromosome 3p. Haplotype analysis defined the locus to a 13.8-cM interval with a LOD score of 5.04. This is the first description of a monogenic form of cutaneous lupus erythematosus. Identification of the gene responsible for familial chilblain lupus may shed light on the pathogenesis of common forms of connective-tissue disease such as systemic lupus erythematosus.

Respiratory chain deficiency in a female with Aicardi-Goutières syndrome

Aicardi-Goutières syndrome (AGS) is an early-onset progressive encephalopathy characterized by calcifications of the basal ganglia, white matter abnormalities, chronic cerebrospinal fluid (CSF) lymphocytosis, and/or a raised level of CSF interferon (INF)-alpha. We report a female with mitochondrial respiratory chain deficiency fulfilling the criteria of AGS. Disease onset was in the first year of age with seizures and psychomotor regression. To date, at 4 years of age, she presents a severe encephalopathy, increased INF-alpha in the CSF, and calcifications of basal ganglia on computerized tomography. Cerebral magnetic resonance imaging showed bilateral and symmetric hypersignal of the posterior white matter. A complex I deficiency of the mitochondrial respiratory chain was found in skeletal muscle, which was associated with a complex IV deficiency in cultured skin fibroblasts. The question of whether this oxidative phosphorylation deficiency is primary or secondary in AGS is open to debate. We suggest giving consideration to systematic evaluation of the mitochondrial respiratory chain in skeletal muscle and skin fibroblasts of other AGS patients.

Elevated interferon-alpha in fetal blood in the prenatal diagnosis of Aicardi-Goutières syndrome

A case of Aicardi-Goutières syndrome is described in a family with index cases. The diagnosis was made prenatally based on high fetal blood concentration of interferon alpha. The biological measurement could be of interest for further diagnosis of other cases.

Heredofamilial brain calcinosis syndrome

Brain calcinosis syndrome (BCS) usually is defined as bilateral calcium accumulation in the brain parenchyma, primarily in the basal ganglia. More than 50 reported clinical conditions have been associated with BCS. We reviewed clinical, radiological, and genetic features of heredofamilial BCS accompanying all conditions associated with calcium accumulation in the brain reported in English between 1962 and 2003 in MEDLINE. The location, extent, and degree of calcification in the brain show diversity not only among the various disorders but also among patients sharing the same condition. The pathogenesis of BCS is uncertain. More complicated mechanisms may be Involved when brain calcinosis is present but calcium, phosphorus, and parathyroid hormone metabolism abnormalities are absent. We review conditions associated with heredofamilial BCS in which brain calcinosis is nearly uniformly present because such information may be Important to the clinician pursuing an investigative strategy.

Aicardi-Goutières syndrome

Aicardi-Goutieres syndrome is a familial progressive early onset encephalopathy with basal ganglia calcifications, chronic CSF lymphocytosis and high level of interferon-alpha in CSF. Cutaneous necrotic lesions and the neuropathological aspect of microangiopathy and microinfarctions suggest a vascular process in relation to elevated interferon-alpha. A genetic defect in the regulation of its synthesis may be the causal factor of the disorder.

Le syndrome d’Aicardi-Goutières : une maladie neurologique infantile, à transmission familiale, encore méconnue

INTRODUCTION

Aicardi-Goutieres syndrome, first described in 1984, is a progressive infantile familial encephalopathy featuring cerebral calcifications, mainly of the basal ganglia, cerebral white matter abnormalities and cerebrospinal fluid lymphocytosis. Most of the patients present with severe developmental retardation, microcephaly, abnormal eye movements, pyramidal tract signs, and prominent dystonic movements. An elevated level of interferon-alpha in the CSF is a constant feature, particularly during the first stages of the disease course. One locus has been mapped on chromosome 3p21 in about half of the families so far studied.

PATIENTS

and results. We report two new French cases and discuss the limits of the clinical syndrome, the differential diagnosis and issues raised by the pathophysiological mechanisms involved. The major concern is to separate this condition from intrauterine infections because of the genetic and therapeutic consequences. A number of other questions remain unanswered. For example, we still do not know today at what age the absence of features like CSF lymphocytosis, and possibly absence of calcifications, rules out the diagnosis of the condition. The origin of the vasculitis lesions is not known, but seems to be related to dysregulation of interferon production and secretion.

CONCLUSION

Currently about 75 patients have been reported, even though many more probably exist. The study of this syndrome can contribute to the understanding of some mechanisms of CNS calcification and in a broader perspective to that of chronic encephalopathies with dysregulation of immune mechanisms.

Tools for diagnosis of leukodystrophies and other disorders presenting with white matter disease

Advances in biochemical techniques, molecular genetics, and neuroimaging, particularly magnetic resonance imaging, have made possible the diagnosis of a significant proportion of leukodystrophies. A specific diagnosis allows the physician to give prognostic information, monitor for known complications, and ultimately may allow disease specific therapeutics. The purpose of this review is to familiarize the reader with pertinent tools in the diagnosis of leukodystrophies and other white matter disorders that may present with white matter disease. The first section discusses conditions that may mimic leukodystrophy and how to exclude them. Although not meant to be an exhaustive summary, several key disorders and their clinical, biochemical, and neuroimaging features are presented. The second section focuses on classically described leukodystrophies and their diagnosis. Finally, a third section provides a diagnostic algorithm to help the clinician in the diagnosis of the patient with leukodystrophy.

Síndrome de Aicardi-Goutières: aportación de dos nuevas observaciones

INTRODUCTION

Aicardi-Goutières syndrome is an early onset autosomal recessive progressive encephalopathy, clinically characterized by acquired microcephaly, severe psychomotor delay and involvement of pyramidal and extrapyramidal tracts. Intracranial calcifications, especially at the level of the basal ganglia, white matter abnormalities, lymphocytosis and raised interferon (IFN)-alpha in blood and cerebrospinal fluid (CSF) form part of this syndrome.

CASES REPORTS

We describe two unrelated infants (a 3-month-old boy and an 11-month-old girl) who both presented with hypotonia, microcephaly, and psychomotor delay. Mild choreic and dystonic movements, as well as progressive spasticity, were also observed in the girl. Extensive investigations revealed intracranial calcifications, mild CSF lymphocytosis in the boy, and raised IFN-a in blood and CSF in both patients.

COMMENTS

Aicardi-Goutières syndrome should be kept in mind when investigating microcephalic and retarded patients with cerebral calcifications initially suggestive of TORCH infection. Appropriate genetic counseling should be provided.

Prenatal diagnosis of Aicardi-Goutières syndrome

OBJECTIVES

Aicardi-Goutières syndrome is an autosomal recessive neurodegenerative disorder inducing cerebral atrophy, intracerebral calcification and developmental arrest. Diagnosis requires the presence of progressive encephalopathy with clinical onset shortly after birth, typical neuroimaging features associated with a raised blood and cerebrospinal fluid interferon-alpha level.A case of prenatal diagnosis of Aicardi-Goutières syndrome is reported.

METHODS

An MRI performed at 26 gestational weeks showed bilateral calcifications and white matter abnormalities, cerebral anomalies typically described in this disease. The fetal blood analysis revealed an increase in interferon-alpha.

RESULTS

Therefore, the prenatal diagnosis of Aicardi-Goutières syndrome in this fetus was based on the following facts: the familial background with the affected first child and consanguineous parents, a normal pregnancy and normal fetal growth, cerebral anomalies diagnosed on prenatal ultrasound and cerebral MRI, raised interferon-alpha in the fetal serum and no evidence of any infectious etiology. The autopsy performed postdelivery at 28 1/2 weeks' gestation confirmed the diagnosis of Aicardi-Goutières syndrome.

CONCLUSION

To the best of our knowledge, this is the first prenatal diagnosis of this syndrome. Such a diagnosis may prove useful for families at risk as long as genetic screening is not available.

Severe fetal brain dysgenesis with focal calcification

OBJECTIVE

To describe a fetal syndrome of abnormal brain development with intracranial calcification, identified in three successive pregnancies.

METHODS

Clinical, imaging, and pathological descriptions, and pedigree assessment.

RESULTS

All three affected pregnancies were terminated, following imaging diagnosis of brain abnormality. The most complete fetal study, from the third of these pregnancies, showed widespread foci of brain calcification not associated with inflammation, with extensive necrosis and calcification of periventricular white matter, but with sparing of thalamus and basal ganglia. The corticospinal tracts were severely hypoplastic.

CONCLUSION

This condition appears to be a 'new' genetically determined, probably autosomal recessive disorder of severe early brain dysgenesis with focal calcification, resembling, but distinct from, certain other clinical genetic entities of which brain calcification is a part.

Congenital glaucoma and brain stem atrophy as features of Aicardi-Goutières syndrome

We report on three children from two families with Aicardi-Goutières syndrome. All three had congenital glaucoma. Additionally, neuroimaging demonstrated significant brain stem atrophy in the affected sib-pair. These features have not been previously described in Aicardi-Goutières syndrome and expand the phenotypic spectrum.