Neuroradiologic patterns and novel imaging findings in Aicardi-Goutières syndrome

Two siblings with Fanconi anemia (FANCQ, ERCC4/XPF) presenting with tumor-mimicking lesions in the brain and acute neurological deterioration

The complementation Q group (FANCQ) subtype of Fanconi anemia (FA) caused by the ERCC4/XPF mutation is very rare. Two siblings, aged 13 and 10 with Fanconi phenotypic features, presented with right hemiparesis and focal-onset seizures. In both cases, cranial magnetic resonance imaging (MRI) showed mass-like lesions accompanied by peripheral edema and calcification. In one case, oral steroid treatment and surgical excision were performed, while in the other case, the cranial lesion regressed just with steroid treatment and without surgery. Both siblings remained wheelchair-bound due to neurological dysfunction. One case died due to hepatocellular carcinoma. ERCC4/XPF gene mutation was detected in both siblings.

Imaging Review of Pediatric Monogenic CNS Vasculopathy with Genetic Correlation

Monogenic cerebral vasculopathy is a rare but progressively recognizable cause of pediatric cerebral vasculopathy manifesting as early as fetal life. These monogenic cerebral vasculopathies can be silent or manifest variably as fetal or neonatal distress, neurologic deficit, developmental delay, cerebral palsy, seizures, or stroke. The radiologic findings can be nonspecific, but the presence of disease-specific cerebral and extracerebral imaging features can point to a diagnosis and guide genetic testing, allowing targeted treatment. The authors review the existing literature describing the frequently encountered and rare monogenic cerebral vascular disorders affecting young patients and describe the relevant pathogenesis, with an attempt to categorize them based on the defective step in vascular homeostasis and/or signaling pathways and characteristic cerebrovascular imaging findings. The authors also highlight the role of imaging and a dedicated imaging protocol in identification of distinct cerebral and extracerebral findings crucial in the diagnostic algorithm and selection of genetic testing. Early and precise recognition of these entities allows timely intervention, preventing or delaying complications and thereby improving quality of life. It is also imperative to identify the specific pathogenic variant and pattern of inheritance for satisfactory genetic counseling and care of at-risk family members. Last, the authors present an image-based approach to these young-onset monogenic cerebral vasculopathies that is guided by the size and predominant radiologic characteristics of the affected vessel with reasonable overlap. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

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.

Nucleotide metabolism, leukodystrophies, and CNS pathology

The balance between a protective and a destructive immune response can be precarious, as exemplified by inborn errors in nucleotide metabolism. This class of inherited disorders, which mimics infection, can result in systemic injury and severe neurologic outcomes. The most common of these disorders is Aicardi Goutières syndrome (AGS). AGS results in a phenotype similar to "TORCH" infections (Toxoplasma gondii, Other [Zika virus (ZIKV), human immunodeficiency virus (HIV)], Rubella virus, human Cytomegalovirus [HCMV], and Herpesviruses), but with sustained inflammation and ongoing potential for complications. AGS was first described in the early 1980s as familial clusters of "TORCH" infections, with severe neurology impairment, microcephaly, and basal ganglia calcifications (Aicardi & Goutières, Ann Neurol, 1984;15:49-54) and was associated with chronic cerebrospinal fluid (CSF) lymphocytosis and elevated type I interferon levels (Goutières et al., Ann Neurol, 1998;44:900-907). Since its first description, the clinical spectrum of AGS has dramatically expanded from the initial cohorts of children with severe impairment to including individuals with average intelligence and mild spastic paraparesis. This broad spectrum of potential clinical manifestations can result in a delayed diagnosis, which families cite as a major stressor. Additionally, a timely diagnosis is increasingly critical with emerging therapies targeting the interferon signaling pathway. Despite the many gains in understanding about AGS, there are still many gaps in our understanding of the cell-type drivers of pathology and characterization of modifying variables that influence clinical outcomes and achievement of timely diagnosis.

Clinical and neuroimaging review of monogenic cerebral small vessel disease from the prenatal to adolescent developmental stage

Cerebral small vessel disease (cSVD) refers to a group of pathological processes with various etiologies affecting the small vessels of the brain. Most cases are sporadic, with age-related and hypertension-related sSVD and cerebral amyloid angiopathy being the most prevalent forms. Monogenic cSVD accounts for up to 5% of causes of stroke. Several causative genes have been identified. Sporadic cSVD has been widely studied whereas monogenic cSVD is still poorly characterized and understood. The majority of cases of both the sporadic and monogenic types, including cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), typically have their onset in adulthood. Types of cSVD with infantile and childhood onset are rare, and their diagnosis is often challenging. The present review discusses the clinical and neuroimaging findings of monogenic cSVD from the prenatal to adolescent period of development. Early diagnosis is crucial to enabling timely interventions and family counseling.

Godoy LF, Pessoa A, A. Costa L, C. Monti F, Souza-Cabral K, Listik C, Castro D, Della-Ripa B, Freua F, C. Pires L, T. Krüger L, D. Gherpelli JL, B. Piazzon F, P. Monteiro F, T. Lucato L, Kok F. Subacute Partially Reversible Leukoencephalopathy Expands the Aicardi-Goutières Syndrome Phenotype

OBJECTIVE

To report a series of atypical presentations of Aicardi-Goutières syndrome.

METHODS

Clinical, neuroimaging, and genetic data.

RESULTS

We report a series of six unrelated patients (five males) with a subacute loss of developmental milestones, pyramidal signs, and regression of communication abilities, with onset at ages ranging from 7 to 20 months, reaching a nadir after 4 to 24 weeks. A remarkable improvement of lost abilities occurred in the follow-up, and they remained with residual spasticity and dysarthria but preserved cognitive function. Immunization or febrile illness occurred before disease onset in all patients. CSF was normal in two patients, and in four, borderline or mild lymphocytosis was present. A brain CT scan disclosed a subtle basal ganglia calcification in one of six patients. Brain MRI showed asymmetric signal abnormalities of white matter with centrum semi-ovale involvement in five patients and a diffuse white matter abnormality with contrast enhancement in one. Four patients were diagnosed and treated for acute demyelinating encephalomyelitis (ADEM). Brain imaging was markedly improved with one year or more of follow-up (average of 7 years), but patients remained with residual spasticity and dysarthria without cognitive impairment. Demyelination relapse occurred in a single patient four years after the first event. Whole-exome sequencing (WES) was performed in all patients: four of them disclosed biallelic pathogenic variants in RNASEH2B (three homozygous p.Ala177Thr and one compound heterozygous p.Ala177Thr/p.Gln58*) and in two of them the same homozygous deleterious variants in RNASEH2A (p.Ala249Val).

CONCLUSIONS

This report expands the phenotype of AGS to include subacute developmental regression with partial clinical and neuroimaging improvement. Those clinical features might be misdiagnosed as ADEM.

Clinical spectrum and currently available treatment of type I interferonopathy Aicardi-Goutières syndrome

BACKGROUND

Aicardi-Goutières syndrome (AGS) is a genetically determined disorder with a variable phenotype. Since the original description of AGS, advances in gene sequencing techniques have resulted in a significant broadening of the phenotypic spectrum associated with AGS genes, and new clinical pictures have emerged beyond the classic presentation. The aim of this review is to provide a comprehensive analysis of the clinical spectrum of AGS and report currently available treatments and new immunosuppressive strategies.

DATA SOURCES

Literature reviews and original research articles were collected from databases, including PubMed and ClinicalTrials.gov. Relevant articles about AGS were included.

RESULTS

The involvement of the nervous system certainly represents the major cause of mortality and morbidity in AGS patients. However, other clinical manifestations, such as chilblains, hepatosplenomegaly, and hematological disturbances, may lead to the diagnosis and considerably impact the prognosis and overall quality of life of these patients. Therapeutic approaches of AGS are limited to interventions aimed at specific symptoms and the management of multiple comorbidities. However, advances in understanding the pathogenesis of AGS could open new and more effective therapies.

CONCLUSIONS

The over-activation of innate immunity due to upregulated interferon production plays a critical role in AGS, leading to multi-organ damage with the main involvement of the central nervous system. To date, there is no specific and effective treatment for AGS. New drugs specifically targeting the interferon pathway may bring new hope to AGS patients.

Breaking down the cellular responses to type I interferon neurotoxicity in the brain

Since their original discovery, type I interferons (IFN-Is) have been closely associated with antiviral immune responses. However, their biological functions go far beyond this role, with balanced IFN-I activity being critical to maintain cellular and tissue homeostasis. Recent findings have uncovered a darker side of IFN-Is whereby chronically elevated levels induce devastating neuroinflammatory and neurodegenerative pathologies. The underlying causes of these 'interferonopathies' are diverse and include monogenetic syndromes, autoimmune disorders, as well as chronic infections. The prominent involvement of the CNS in these disorders indicates a particular susceptibility of brain cells to IFN-I toxicity. Here we will discuss the current knowledge of how IFN-Is mediate neurotoxicity in the brain by analyzing the cell-type specific responses to IFN-Is in the CNS, and secondly, by exploring the spectrum of neurological disorders arising from increased IFN-Is. Understanding the nature of IFN-I neurotoxicity is a crucial and fundamental step towards development of new therapeutic strategies for interferonopathies.

Case report: Pneumocystis jirovecii pneumonia in a severe case of Aicardi-Goutières syndrome with an IFIH1 gain-of-function mutation mimicking combined immunodeficiency

Aicardi-Goutières syndrome (AGS) is a genetically determined early-onset progressive encephalopathy caused by mutations leading to overexpression of type I interferon (IFN) and resulting in various clinical phenotypes. A gain-of-function (GOF) mutation in the IFIH1 gene is associated with robust production of type I IFN and activation of the Janus kinase (JAK) signal transducer and activator of the transcription (STAT) pathway, which can cause AGS type 7. We detail the clinical case of an infant who initially presented with Pneumocystis jirovecii pneumonia (PCP), had recurrent respiratory infections, and was later treated with a JAK inhibitor, baricitinib, because of a genetically confirmed GOF mutation in the IFIH1 gene. This spectrum of IFIH1 GOF mutations with overlapping features of hyperinflammation and severe opportunistic infection, which mimics combined immunodeficiency (CID), has not been described before. In this case, therapy with baricitinib effectively blocked IFN-α activation and reduced STAT1 signaling but had no effect on the progression of the neurological disease.

Infection and inflammation: radiological insights into patterns of pediatric immune-mediated CNS injury

The central nervous system (CNS) undergoes constant immune surveillance enabled via regionally specialized mechanisms. These include selectively permissive barriers and modifications to interlinked innate and adaptive immune systems that detect and remove an inciting trigger. The end-points of brain injury and edema from these triggers are varied but often follow recognizable patterns due to shared underlying immune drivers. Imaging provides insights to understanding these patterns that often arise from unique interplays of infection, inflammation and genetics. We review the current updates in our understanding of these intersections and through examples of cases from our practice, highlight that infection and inflammation follow diverse yet convergent mechanisms that can challenge the CNS in children.

Child Neurology: Aicardi-Goutières Syndrome Presenting as Recurrent Ischemic Stroke

Aicardi-Goutières syndrome (AGS) is a rare, single-gene disorder, characterized by neurological and skin involvement with an increased level of interferon-α (IFN-α) in the cerebrospinal fluid (CSF). We describe the case of a young patient presenting with recurrent ischemic stroke. Evaluation revealed the presence of chilblains, white matter abnormalities, cerebral atrophy, and raised IFN-α in the CSF. Compound heterozygous variants of TREX1 were detected, confirming a diagnosis of AGS. After excluding other causes, we attributed the stroke to AGS. Tofacitinib, a Janus kinase (JAK) inhibitor, was administered to our patient in addition to antiplatelet drugs. There was no recurrence of stroke during 3-month follow-up. This is the first description of recurrent stroke in TREX1-mutated AGS. Small vessel involvement has been previously demonstrated to play a significant role in the pathogenesis of AGS. This microvascular mechanism might explain the occurrence of ischemic stroke in our patient. For young stroke patients with multiple system involvement, genetic disorders including AGS should be considered.

Mutations in RNU7-1 Weaken Secondary RNA Structure, Induce MCP-1 and CXCL10 in CSF, and Result in Aicardi-Goutières Syndrome with Severe End-Organ Involvement

BACKGROUND

Aicardi-Goutières syndrome (AGS) is a type I interferonopathy usually characterized by early-onset neurologic regression. Biallelic mutations in LSM11 and RNU7-1, components of the U7 small nuclear ribonucleoprotein (snRNP) complex, have been identified in a limited number of genetically unexplained AGS cases. Impairment of U7 snRNP function results in misprocessing of replication-dependent histone (RDH) pre-mRNA and disturbance of histone occupancy of nuclear DNA, ultimately driving cGAS-dependent type I interferon (IFN-I) release.

OBJECTIVE

We performed a clinical, genetic, and immunological workup of 3 unrelated patients with uncharacterized AGS.

METHODS

Whole exome sequencing (WES) and targeted Sanger sequencing of RNU7-1 were performed. Primary fibroblasts were used for mechanistic studies. IFN-I signature and STAT1/2 phosphorylation were assessed in peripheral blood. Cytokines were profiled on serum and cerebrospinal fluid (CSF). Histopathology was examined on brain and kidney tissue.

RESULTS

Sequencing revealed compound heterozygous RNU7-1 mutations, resulting in impaired RDH pre-mRNA processing. The 3' stem-loop mutations reduced stability of the secondary U7 snRNA structure. A discrete IFN-I signature in peripheral blood was paralleled by MCP-1 (CCL2) and CXCL10 upregulation in CSF. Histopathological analysis of the kidney showed thrombotic microangiopathy. We observed dysregulated STAT phosphorylation upon cytokine stimulation. Clinical overview of all reported patients with RNU7-1-related disease revealed high mortality and high incidence of organ involvement compared to other AGS genotypes.

CONCLUSIONS

Targeted RNU7-1 sequencing is recommended in genetically unexplained AGS cases. CSF cytokine profiling represents an additional diagnostic tool to identify aberrant IFN-I signaling. Clinical follow-up of RNU7-1-mutated patients should include screening for severe end-organ involvement including liver disease and nephropathy.

The 2021 European Alliance of Associations for Rheumatology/American College of Rheumatology Points to Consider for Diagnosis and Management of Autoinflammatory Type I Interferonopathies: CANDLE/PRAAS, SAVI, and AGS

OBJECTIVE

Autoinflammatory type I interferonopathies, chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature/proteasome-associated autoinflammatory syndrome (CANDLE/PRAAS), stimulator of interferon genes (STING)-associated vasculopathy with onset in infancy (SAVI), and Aicardi-Goutières syndrome (AGS) are rare and clinically complex immunodysregulatory diseases. With emerging knowledge of genetic causes and targeted treatments, a Task Force was charged with the development of "points to consider" to improve diagnosis, treatment, and long-term monitoring of patients with these rare diseases.

METHODS

Members of a Task Force consisting of rheumatologists, neurologists, an immunologist, geneticists, patient advocates, and an allied health care professional formulated research questions for a systematic literature review. Then, based on literature, Delphi questionnaires, and consensus methodology, "points to consider" to guide patient management were developed.

RESULTS

The Task Force devised consensus and evidence-based guidance of 4 overarching principles and 17 points to consider regarding the diagnosis, treatment, and long-term monitoring of patients with the autoinflammatory interferonopathies, CANDLE/PRAAS, SAVI, and AGS.

CONCLUSION

These points to consider represent state-of-the-art knowledge to guide diagnostic evaluation, treatment, and management of patients with CANDLE/PRAAS, SAVI, and AGS and aim to standardize and improve care, quality of life, and disease outcomes.

The 2021 EULAR and ACR points to consider for diagnosis and management of autoinflammatory type I interferonopathies: CANDLE/PRAAS, SAVI and AGS

OBJECTIVE

Autoinflammatory type I interferonopathies, chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature/proteasome-associated autoinflammatory syndrome (CANDLE/PRAAS), stimulator of interferon genes (STING)-associated vasculopathy with onset in infancy (SAVI) and Aicardi-Goutières syndrome (AGS) are rare and clinically complex immunodysregulatory diseases. With emerging knowledge of genetic causes and targeted treatments, a Task Force was charged with the development of 'points to consider' to improve diagnosis, treatment and long-term monitoring of patients with these rare diseases.

METHODS

Members of a Task Force consisting of rheumatologists, neurologists, an immunologist, geneticists, patient advocates and an allied healthcare professional formulated research questions for a systematic literature review. Then, based on literature, Delphi questionnaires and consensus methodology, 'points to consider' to guide patient management were developed.

RESULTS

The Task Force devised consensus and evidence-based guidance of 4 overarching principles and 17 points to consider regarding the diagnosis, treatment and long-term monitoring of patients with the autoinflammatory interferonopathies, CANDLE/PRAAS, SAVI and AGS.

CONCLUSION

These points to consider represent state-of-the-art knowledge to guide diagnostic evaluation, treatment and management of patients with CANDLE/PRAAS, SAVI and AGS and aim to standardise and improve care, quality of life and disease outcomes.

Spectrum of Neuroradiologic Findings Associated with Monogenic Interferonopathies

The genetic interferonopathies are a heterogeneous group of disorders thought to be caused by the dysregulated expression of interferons and are now commonly considered in the differential diagnosis of children presenting with recurrent or persistent inflammatory phenotypes. With emerging therapeutic options, recognition of these disorders is increasingly important, and neuroimaging plays a vital role. In this article, we discuss the wide spectrum of neuroradiologic features associated with monogenic interferonopathies by reviewing the literature and illustrate these with cases from our institutions. These cases include intracerebral calcifications, white matter T2 hyperintensities, deep WM cysts, cerebral atrophy, large cerebral artery disease, bilateral striatal necrosis, and masslike lesions. A better understanding of the breadth of the neuroimaging phenotypes in conjunction with clinical and laboratory findings will enable earlier diagnosis and direct therapeutic strategies.

Aicardi-Goutières Syndrome due to a Mutation Presenting with Deep White Matter Cysts

We report on the first Polish patient diagnosed with the Aicardi-Goutières syndrome 5 (AGS5). AGS is caused by mutations in one of 9 genes (<i>TREX1</i>, <i>RNASEH2A</i>, <i>RNASEH2B</i>, <i>RNASEH2C</i>, <i>SAMHD1</i>, <i>ADAR</i>, <i>IFIH</i>, <i>LSM11</i>, <i>RNU7-1</i>) which stimulate the type I interferon response. The diagnosis was confirmed by identifying a compound heterozygous mutation p.(Phe165Ser)/p.(Gln235*) in the <i>SAMHD1</i> gene using whole-exome sequencing. The cystic lesions in the temporal lobes are an uncommon finding in the presented patient carrying a <i>SAMHD1</i> mutation. Reporting new cases expands the range of phenotypes and plays the crucial role in understanding the AGS pathogenesis and creates new therapy approaches.

Leukodystrophies in Children: Diagnosis, Care, and Treatment

Leukodystrophies are a group of genetically determined disorders that affect development or maintenance of central nervous system myelin. Leukodystrophies have an incidence of at least 1 in 4700 live births and significant morbidity and elevated risk of early death. This report includes a discussion of the types of leukodystrophies; their prevalence, clinical presentation, symptoms, and diagnosis; and current and future treatments. Leukodystrophies can present at any age from infancy to adulthood, with variability in disease progression and clinical presentation, ranging from developmental delay to seizures to spasticity. Diagnosis is based on a combination of history, examination, and radiologic and laboratory findings, including genetic testing. Although there are few cures, there are significant opportunities for care and improvements in patient well-being. Rapid advances in imaging and diagnosis, the emergence of and requirement for timely treatments, and the addition of leukodystrophy screening to newborn screening, make an understanding of the leukodystrophies necessary for pediatricians and other care providers for children.

Monogenic Autoinflammatory Diseases: State of the Art and Future Perspectives

Systemic autoinflammatory diseases are a heterogeneous family of disorders characterized by a dysregulation of the innate immune system, in which sterile inflammation primarily develops through antigen-independent hyperactivation of immune pathways. In most cases, they have a strong genetic background, with mutations in single genes involved in inflammation. Therefore, they can derive from different pathogenic mechanisms at any level, such as dysregulated inflammasome-mediated production of cytokines, intracellular stress, defective regulatory pathways, altered protein folding, enhanced NF-kappaB signalling, ubiquitination disorders, interferon pathway upregulation and complement activation. Since the discover of pathogenic mutations of the pyrin-encoding gene MEFV in Familial Mediterranean Fever, more than 50 monogenic autoinflammatory diseases have been discovered thanks to the advances in genetic sequencing: the advent of new genetic analysis techniques and the discovery of genes involved in autoinflammatory diseases have allowed a better understanding of the underlying innate immunologic pathways and pathogenetic mechanisms, thus opening new perspectives in targeted therapies. Moreover, this field of research has become of great interest, since more than a hundred clinical trials for autoinflammatory diseases are currently active or recently concluded, allowing us to hope for considerable acquisitions for the next few years. General paediatricians need to be aware of the importance of this group of diseases and they should consider autoinflammatory diseases in patients with clinical hallmarks, in order to guide further examinations and refer the patient to a specialist rheumatologist. Here we resume the pathogenesis, clinical aspects and diagnosis of the most important autoinflammatory diseases in children.

Ruxolitinib in Aicardi-Goutières syndrome

Aicardi-Goutières Syndrome (AGS) is a monogenic leukodystrophy with pediatric onset, clinically characterized by a variable degree of neurologic impairment. It belongs to a group of condition called type I interferonopathies that are characterized by abnormal overproduction of interferon alpha, an inflammatory cytokine which action is mediated by the activation of two of the four human Janus Kinases. Thanks to an ever-increasing knowledge of the molecular basis and pathogenetic mechanisms of the disease, Janus Kinase inhibitors (JAKIs) have been proposed as a treatment option for selected interferonopathies. Here we reported the 24 months follow-up of the fifth AGS patient treated with ruxolitinib described so far in literature. The treatment was globally well tolerated; clinical examinations and radiological images demonstrated a progressively improving course. It is however to note that patients presenting with mild and spontaneously improving course have been reported. Large natural history studies on AGS spectrum are strongly required in order to get a better understanding of the results emerging from ongoing therapeutic trials on such rare disease.

The epileptology of Aicardi-Goutières syndrome: electro-clinical-radiological findings

OBJECTIVE

Although epileptic seizures occur in approximately a quarter of patients with Aicardi-Goutières syndrome (AGS), their phenotypic and electrophysiological characterization remains elusive. The aim of our study was to characterize epilepsy phenotypes and electroencephalographic (EEG) patterns in AGS and look for possible correlations with clinical, genetic and neuroradiological features.

METHODS

We selected patients with an established AGS diagnosis followed at three Italian reference centers. Medical records, EEGs and MRI/CT findings were reviewed. EEGs were independently and blindly reviewed by three board-certified pediatric epileptologists. Chi square and Fisher's exact tests were used to test associations between epilepsy and EEG feature categories and clinical, radiological and genetic variables.

RESULTS

Twenty-seven patients were enrolled. We reviewed 63 EEGs and at least one brain MRI scan per patient. Epilepsy, mainly in the form of epileptic spasms and focal seizures, was present in 37 % of the cohort; mean age at epilepsy onset was 9.5 months (range 1-36). The presence of epilepsy was associated with calcification severity (p = 0.016) and startle reactions (p = 0.05). Organization of EEG electrical activity appeared to be disrupted or markedly disrupted in 73 % of cases. Severe EEG disorganization correlated with microcephaly (p < 0.001) and highly abnormal MRI T2-weighted signal intensity in white matter (p = 0.022). Physiological organization of the EEG was found to be better preserved during sleep (87 %) than wakefulness (38 %). Focal slow activity was recorded in more than one third of cases. Fast activity, either diffuse or with frontal location, was more frequent in the awake state (78 %) than in sleep (50 %). Interictal epileptiform discharges (IEDs) were present in 33 % of awake and 45 % of sleep recordings. IEDs during sleep were associated with a higher risk of a epileptic seizures (p = 0.008).

SIGNIFICANCE

The hallmarks of EEG recordings in AGS were found to be: disruption of electrical organization, the presence of focal slow and fast activity, and the presence of IEDs, both in patients with and in those without epilepsy. The associations between epilepsy and calcification and between EEG pattern and the finding of a highly abnormal white matter T2 signal intensity suggest a common anatomical correlate. However, the complex anatomical-electroclinical basis of AGS-related epilepsy still requires further elucidation.

PNPT1 mutations may cause Aicardi-Goutières-Syndrome

BACKGROUND

Aicardi-Goutières syndrome (AGS) is a clinically and genetically heterogenous autoinflammatory disorder caused by constitutive activation of the type I interferon axis. It has been associated with the genes TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR1, IFIH1. The clinical diagnosis of AGS is usually made in the context of early-onset encephalopathy in combination with basal ganglia calcification or white matter abnormalities on cranial MRI and laboratory prove of interferon I activation.

CASE PRESENTATION

We report a patient with early-onset encephalopathy, severe neurodevelopmental regression, progressive secondary microcephaly, epilepsy, movement disorder, and white matter hyperintensities on T2 weighted MRI images. Via whole-exome sequencing, we identified a novel homozygous missense variant (c.1399C > T, p.Pro467Ser) in PNPT1 (NM_033109). Longitudinal assessment of the interferon signature showed a massively elevated interferon score and chronic type I interferon-mediated autoinflammation.

CONCLUSION

Bi-allelic mutations in PNPT1 have been reported in early-onset encephalopathy. Insufficient nuclear RNA import into mitochondria with consecutive disruption of the respiratory chain was proposed as the main underlying pathomechanism. Recent studies have shown that PNPT1 deficiency causes an accumulation of double-stranded mtRNAs in the cytoplasm, leading to aberrant type I interferon activation, however, longitudinal assessment has been lacking. Here, we present a case of AGS with continuously elevated type I interferon signature with a novel likely-pathogenic homozygous PNTP1 variant. We highlight the clinical value of assessing the interferon signature in children with encephalopathy of unknown origin and suggest all patients presenting with a phenotype of AGS should be screened for mutations in PNPT1.

Late-Onset Aicardi-Goutières Syndrome: A Characterization of Presenting Clinical Features

BACKGROUND

Aicardi-Goutières syndrome (AGS) is a genetic interferonopathy characterized by early onset of severe neurological injury with intracranial calcifications, leukoencephalopathy, and systemic inflammation. Increasingly, a spectrum of neurological dysfunction and presentation beyond the infantile period is being recognized in AGS. The aim of this study was to characterize late-infantile and juvenile-onset AGS.

METHODS

We conducted a multi-institution review of individuals with AGS who were older than one year at the time of presentation, including medical history, imaging characteristics, and suspected diagnoses at presentation.

RESULTS

Thirty-four individuals were identified, all with pathogenic variants in RNASEH2B, SAMHD1, ADAR1, or IFIH1. Most individuals had a history of developmental delay and/or systemic symptoms, such as sterile pyrexias and chilblains, followed by a prodromal period associated with increasing symptoms. This was followed by an abrupt onset of neurological decline (fulminant phase), with a median onset at 1.33 years (range 1.00 to 17.68 years). Most individuals presented with a change in gross motor skills (97.0%), typically with increased tone (78.8%). Leukodystrophy was the most common magnetic resonance imaging finding (40.0%). Calcifications were less common (12.9%).

CONCLUSIONS

This is the first study to characterize the presentation of late-infantile and juvenile onset AGS and its phenotypic spectrum. Late-onset AGS can present insidiously and lacks classical clinical and neuroimaging findings. Signs of early systemic dysfunction before fulminant disease onset and loss of motor symptoms were common. We strongly recommend genetic testing when there is concern for sustained inflammation of unknown origins or changes in motor skills in children older than one year.

Congenital Zika syndrome: A systematic review

BACKGROUND

The signs and symptoms of Zika virus infection are usually mild and self-limited. However, the disease has been linked to neurological complications such as Guillain-Barré syndrome and peripheral nerve involvement, and also to abortion and fetal deaths due to vertical transmission, resulting in various congenital malformations in newborns, including microcephaly. This review aimed to describe the o signs and symptoms that characterize the congenital Zika syndrome.

METHODS AND FINDINGS

A systematic review was performed with a protocol and described according to the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. The search strategy yielded 2,048 studies. After the exclusion of duplicates and application of inclusion criteria, 46 studies were included. The main signs and symptoms associated with the congenital Zika syndrome were microcephaly, parenchymal or cerebellar calcifications, ventriculomegaly, central nervous system hypoplasia or atrophy, arthrogryposis, ocular findings in the posterior and anterior segments, abnormal visual function and low birthweight for gestational age.

CONCLUSIONS

Zika virus infection during pregnancy can cause a series of changes in the growth and development of children, while impacting the healthcare system due to the severity of cases. Our findings outline the disease profile in newborns and infants and may contribute to the development and updating of more specific clinical protocols.

Overview of STING-Associated Vasculopathy with Onset in Infancy (SAVI) Among 21 Patients

BACKGROUND

Gain-of-function mutations in STING1 underlie a type I interferonopathy termed SAVI (STING-associated vasculopathy with onset in infancy). This severe disease is variably characterized by early-onset systemic inflammation, skin vasculopathy, and interstitial lung disease (ILD).

OBJECTIVE

To describe a cohort of patients with SAVI.

METHODS

Assessment of clinical, radiological and immunological data from 21 patients (17 families) was carried out.

RESULTS

Patients carried heterozygous substitutions in STING1 previously described in SAVI, mainly the p.V155M. Most were symptomatic from infancy, but late onset in adulthood occurred in 1 patient. Systemic inflammation, skin vasculopathy, and ILD were observed in 19, 18, and 21 patients, respectively. Extensive tissue loss occurred in 4 patients. Severity of ILD was highly variable with insidious progression up to end-stage respiratory failure reached at teenage in 6 patients. Lung imaging revealed early fibrotic lesions. Failure to thrive was almost constant, with severe growth failure seen in 4 patients. Seven patients presented polyarthritis, and the phenotype in 1 infant mimicked a combined immunodeficiency. Extended features reminiscent of other interferonopathies were also found, including intracranial calcification, glaucoma and glomerular nephropathy. Increased expression of interferon-stimulated genes and interferon α protein was constant. Autoantibodies were frequently found, in particular rheumatoid factor. Most patients presented with a T-cell defect, with low counts of memory CD8+ cells and impaired T-cell proliferation in response to antigens. Long-term follow-up described in 8 children confirmed the clinical benefit of ruxolitinib in SAVI where the treatment was started early in the disease course, underlying the need for early diagnosis. Tolerance was reasonably good.

CONCLUSION

The largest worldwide cohort of SAVI patients yet described, illustrates the core features of the disease and extends the clinical and immunological phenotype to include overlap with other monogenic interferonopathies.

Heterogeneity of PNPT1 neuroimaging: mitochondriopathy, interferonopathy or both?

BACKGROUND

Biallelic variants in PNPT1 cause a mitochondrial disease of variable severity. PNPT1 (polynucleotide phosphorylase) is a mitochondrial protein involved in RNA processing where it has a dual role in the import of small RNAs into mitochondria and in preventing the formation and release of mitochondrial double-stranded RNA into the cytoplasm. This, in turn, prevents the activation of type I interferon response. Detailed neuroimaging findings in PNPT1-related disease are lacking with only a few patients reported with basal ganglia lesions (Leigh syndrome) or non-specific signs.

OBJECTIVE AND METHODS

To document neuroimaging data in six patients with PNPT1 highlighting novel findings.

RESULTS

Two patients exhibited striatal lesions compatible with Leigh syndrome; one patient exhibited leukoencephalopathy and one patient had a normal brain MRI. Interestingly, two unrelated patients exhibited cystic leukoencephalopathy resembling RNASET2-deficient patients, patients with Aicardi-Goutières syndrome (AGS) or congenital CMV infection.

CONCLUSION

We suggest that similar to RNASET2, PNPT1 be searched for in the setting of cystic leukoencephalopathy. These findings are in line with activation of type I interferon response observed in AGS, PNPT1 and RNASET2 deficiencies, suggesting a common pathophysiological pathway and linking mitochondrial diseases, interferonopathies and immune dysregulations.

A Novel Mutation in Aicardi–Goutières' Syndrome: A Case Report

Aicardi–Goutières' syndrome (AGS) is a rare heterogeneous genetic disorder characterized by encephalopathy and may bear resemblance to congenital infections. The prevalence of AGS is estimated at more than 4,000 worldwide. Mutations in TREX1 gene are present in ∼22% of patients. We present the case of a 2-year-old boy who came to the Biogene laboratory (Tehran, Iran) with a constellation of congenital disorders but no clear diagnosis. His clinical phenotype consisted of neonatal jaundice, relative microcephaly with diffuse cerebral atrophy in both hemispheres, developmental delay, hypotonia, and nystagmus. There was history of parental consanguineous marriage and prematurity. In our study, a homozygous potentially pathogenic mutation in TREX1 gene associated with AGS1 was detected. This mutation has not been reported in the other patients with AGS. A novel frameshift homozygous potentially pathogenic mutation in TREX1 is postulated to be the cause of disease in our patient.

Intracranial calcifications in childhood: Part 2

This article is the second of a two-part series on intracranial calcification in childhood. In Part 1, the authors discussed the main differences between physiological and pathological intracranial calcification. They also outlined histological intracranial calcification characteristics and how these can be detected across different neuroimaging modalities. Part 1 emphasized the importance of age at presentation and intracranial calcification location and proposed a comprehensive neuroimaging approach toward the differential diagnosis of the causes of intracranial calcification. Pathological intracranial calcification can be divided into infectious, congenital, endocrine/metabolic, vascular, and neoplastic. In Part 2, the chief focus is on discussing endocrine/metabolic, vascular, and neoplastic intracranial calcification etiologies of intracranial calcification. Endocrine/metabolic diseases causing intracranial calcification are mainly from parathyroid and thyroid dysfunction and inborn errors of metabolism, such as mitochondrial disorders (MELAS, or mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes; Kearns-Sayre; and Cockayne syndromes), interferonopathies (Aicardi-Goutières syndrome), and lysosomal disorders (Krabbe disease). Specific noninfectious causes of intracranial calcification that mimic TORCH (toxoplasmosis, other [syphilis, varicella-zoster, parvovirus B19], rubella, cytomegalovirus, and herpes) infections are known as pseudo-TORCH. Cavernous malformations, arteriovenous malformations, arteriovenous fistulas, and chronic venous hypertension are also known causes of intracranial calcification. Other vascular-related causes of intracranial calcification include early atherosclerosis presentation (children with risk factors such as hyperhomocysteinemia, familial hypercholesterolemia, and others), healed hematoma, radiotherapy treatment, old infarct, and disorders of the microvasculature such as COL4A1- and COL4A2-related diseases. Intracranial calcification is also seen in several pediatric brain tumors. Clinical and familial information such as age at presentation, maternal exposure to teratogens including viruses, and association with chromosomal abnormalities, pathogenic genes, and postnatal infections facilitates narrowing the differential diagnosis of the multiple causes of intracranial calcification.

Monogenic autoinflammatory diseases in children: single center experience with clinical, genetic, and imaging review

Purpose

1. To review the contemporary literature and present a list of the imaging findings for patients with autoinflammatory diseases from our hospital. All these patients are found to have a genetic mutation that is responsible for their disease.

2. To present follow-up imaging findings, when available, and correlate those with symptoms and type of treatment administered in approximately 40 patients with autoinflammatory diseases of a single tertiary pediatric health care center including familial Mediterranean fever, Cryopyrin-associated autoinflammatory syndrome, PAPA (pyogenic arthritis, pyoderma gangrenousum, and acne) syndrome, and more. These findings are related to disease progression, treatment response, or treatment-induced changes.

Conclusion

Autoinflammatory diseases are relatively rare entities that can affect any system of the body. Given the many nonspecific imaging features, awareness of these diseases and good communication with clinicians aid in reaching an accurate diagnosis.

Evaluation of Physiological Intracranial Calcifications in Children Using Computed Tomography

Introduction. Physiological intracranial calcifications have an increasing prevalence with the age and can be found in both children and in adults. These calcifications are basically asymptomatic and their presence can only be noticed through neuro-imaging.

The aim of the paper was to evaluate physiological intracranial calcifications in children using computed tomography, in our conditions.

Materials and methods. The study was designed as a retrospective, observational, non-randomized clinical study. It was conducted at the Department of Radiology, Clinical Center Kragujevac, Serbia. The study included all the patients scanned by CT from 1st October, 2008. to 30th September, 2018.. The criteria for the inclusion were: the patients aged up to 18 years who underwent a non-contrast computed tomography in the observed period, with diagnosed intracranial calcifications that do not have pathological etiology.

Results. Our study included 420 patients. Out of them, 213 (50.7%) were boys and 207 (49.3%) were girls. The mean age was 12.47. We divided the patients into two age categories: the first one included the patients aged 1 to 10 years and the other one included the patients aged 11 to 18 years. Our study has demonstrated that physiological intracranial calcifications are the most frequent in habenula (28.1%), followed by the pineal gland (22.6%) and choroid plexus (18.8%).

Conclusion. There is a small number of studies with the subject of physiological intracranial calcification distribution, especially in children. It is important to know in which locations we can expect physiological intracranial calcifications, as well as the age in which they become detectable by imaging, in order not to mix them with hemorrhages, pathological tumor or metabolic mineralization.

Solving the hypomyelination conundrum - Imaging perspectives

Hypomyelinating Leukodystrophies (HLDs) are a genetically heterogeneous, clinically overlapping group of disorders with the unifying MR imaging appearance of myelin deficit in the brain. In fact, it is the MRI phenotype that typically raises the diagnostic suspicion in this single largest group of undiagnosed leukodystrophies and guides gene testing for confirmation. This article reviews the neurobiology of myelination, focussing on the complex interplay of molecular genetic pathways and presents a practical clinico-radiological diagnostic algorithm based on the neuroimaging patterns of the common hypomyelinating disorders. The authors also address the current controversies about the definition and use of the term 'hypomyelination'.

Relapsing-remitting clinical course expands the phenotype of Aicardi-Goutières syndrome

Aicardi-Goutières syndrome (AGS) is a rare and likely underdiagnosed genetic leukoencephalopathy, typically presenting in infancy with encephalopathy and characteristic neuroimaging features, with residual static neurological deficits. We describe a patient who, following an initial presentation at the age of 12 months in keeping with AGS, exhibited a highly atypical relapsing course of neurological symptoms in adulthood with essentially normal neuroimaging. Whole-exome sequencing confirmed a pathogenic RNASEH2B gene variant consistent with AGS. This case highlights the expanding phenotypes associated with AGS and the potential role of whole-exome sequencing in facilitating an increase in the rate of diagnosis.

Spontaneous MRI improvement and absence of cerebral calcification in Aicardi-Goutières syndrome: Diagnostic and disease-monitoring implications

BACKGROUND

Aicardi-Goutières syndrome (AGS) is a rare genetic leukoencephalopathy related to inappropriate activation of type I interferon. Neuroradiological findings are typically characterized by white matter abnormalities, cerebral atrophy and cerebral calcification. The disease usually manifests itself during the first year of life in the form of an initial "encephalitic-like" phase followed by a chronic phase of stabilization of the neurological signs. Recently new therapeutic strategies have been proposed aimed at blocking the abnormal activation of the interferon cascade.

MATERIALS AND METHODS

We reviewed clinical and MRI findings in three young RNASEH2B-mutated patients studied with serial CT and MRI studies.

RESULTS

All three patients presented clinical and MRI features consistent with AGS but, very unexpectedly, an improving neuroradiological course. In patient 1, the MRI improvement was noted some months after treatment with high-dose steroid and IVIg treatment; in patients 2 and 3 it occurred spontaneously. Patient 2 did not show cerebral calcification on CT images.

CONCLUSIONS

Our series highlights the possibility of spontaneous neuroradiological improvement in AGS2 patients, as well as the possibility of absence of cerebral calcification in AGS. The study underlines the need for extreme caution when using MRI as an outcome measure in therapeutic trials specific for this disease. MRI follow-up studies in larger series are necessary to describe the natural course of AGS.

Neuropathological Findings in a Case of IFIH1-Related Aicardi-Goutières Syndrome

Aicardi-Goutières syndrome (AGS) is a rare syndrome characterized by calcification, diffuse demyelination, and variable degree of brain atrophy. The syndrome is genetically heterogeneous with mutations in 7 genes, including TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR1, and IFIH1 (interferon-induced helicase c domain-containing protein 1) associated with the syndrome, so far. These mutations lead to the overproduction of α-interferon within the central nervous system. Mutations in IFIH1 have been recently described in a subset of AGS, with only 1 previous report of neuropathological findings. We report neuropathological findings in a second case of AGS with a known mutation in IFIH1 gene. The patient is a 16-year-old adolescent boy with early-onset symptoms that progressed to profound loss of cognitive and motor functions. The patient experienced sudden cardiopulmonary arrest at the age of 16 years. At autopsy, the cause of death was determined to be pulmonary thromboembolism. Neuropathological examination revealed microcephaly (brain weight: 916 g) with relatively mild brain atrophy on gross examination. Microscopic examination revealed multifocal calcifications limited to small to medium central nervous system arteries (no evidence of calcification in other organs), involving bilateral cerebral cortex, basal ganglia, thalamus, and cerebellum. Ultrastructural examination showed Calcospherules limited to the vessel walls and the perivasulcar area without evidence of neuronal ferrugination or tubuloreticular bodies. The extent of calcifications was variable across different brain regions, resembling findings in previously reported cases and correlated with the extent of IFIH1 protein expression (data derived from Allen Brain Institute). AGS is a rare cause of brain calcifications that can closely mimic congenital and neonatal infections such as Rubella and similar infections.

Aicardi goutières syndrome is associated with pulmonary hypertension

While pulmonary hypertension (PH) is a potentially life threatening complication of many inflammatory conditions, an association between Aicardi Goutières syndrome (AGS), a rare genetic cause of interferon (IFN) overproduction, and the development of PH has not been characterized to date. We analyzed the cardiac function of individuals with AGS enrolled in the Myelin Disorders Bioregistry Project using retrospective chart review (n = 61). Additional prospective echocardiograms were obtained when possible (n = 22). An IFN signature score, a marker of systemic inflammation, was calculated through the measurement of mRNA transcripts of type I IFN-inducible genes (interferon signaling genes or ISG). Pathologic analysis was performed as available from autopsy samples. Within our cohort, four individuals were identified to be affected by PH: three with pathogenic gain-of-function mutations in the IFIH1 gene and one with heterozygous TREX1 mutations. All studied individuals with AGS were noted to have elevated IFN signature scores (Mann-Whitney p < .001), with the highest levels in individuals with IFIH1 mutations (Mann-Whitney p < .0001). We present clinical and histologic evidence of PH in a series of four individuals with AGS, a rare interferonopathy. Importantly, IFIH1 and TREX1 may represent a novel cause of PH. Furthermore, these findings underscore the importance of screening all individuals with AGS for PH.

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.

Encephalopathies with intracranial calcification in children: clinical and genetic characterization

Background

We present a group of patients affected by a paediatric onset genetic encephalopathy with cerebral calcification of unknown aetiology studied with Next Generation Sequencing (NGS) genetic analyses.

Methods

We collected all clinical and radiological data. DNA samples were tested by means of a customized gene panel including fifty-nine genes associated with known genetic diseases with cerebral calcification.

Results

We collected a series of fifty patients. All patients displayed complex and heterogeneous phenotypes mostly including developmental delay and pyramidal signs and less frequently movement disorder and epilepsy. Signs of cerebellar and peripheral nervous system involvement were occasionally present. The most frequent MRI abnormality, beside calcification, was the presence of white matter alterations; calcification was localized in basal ganglia and cerebral white matter in the majority of cases. Sixteen out of fifty patients tested positive for mutations in one of the fifty-nine genes analyzed. In fourteen cases the analyses led to a definite genetic diagnosis while results were controversial in the remaining two.

Conclusions

Genetic encephalopathies with cerebral calcification are usually associated to complex phenotypes. In our series, a molecular diagnosis was achieved in 32% of cases, suggesting that the molecular bases of a large number of disorders are still to be elucidated. Our results confirm that cerebral calcification is a good criterion to collect homogeneous groups of patients to be studied by exome or whole genome sequencing; only a very close collaboration between clinicians, neuroradiologists and geneticists can provide better results from these new generation molecular techniques.

Phenotypic and Molecular Spectrum of Aicardi-Goutières Syndrome: A Study of 24 Patients

BACKGROUND

Aicardi-Goutières syndrome is a rare genetic neurological disorder with variable clinical manifestations. Molecular detection of specific mutations is required to confirm the diagnosis. The aim of this study was to review the clinical and molecular diagnostic findings in 24 individuals with Aicardi-Goutières syndrome who presented during childhood in an Arab population.

MATERIALS AND METHODS

We reviewed the records of 24 patients from six tertiary hospitals in different Arab countries. All included patients had a molecular diagnosis of Aicardi-Goutières syndrome.

RESULTS

Six individuals with Aicardi-Goutières syndrome (25%) had a neonatal presentation, whereas the remaining patients presented during the first year of life. Patients presented with developmental delay (24 cases, 100%); spasticity (24 cases, 100%); speech delay (23 cases, 95.8%); profound intellectual disability (21 cases, 87.5%); truncal hypotonia (21 cases, 87.5%); seizures (eighteen cases, 75%); and epileptic encephalopathy (15 cases, 62.5%). Neuroimaging showed white matter abnormalities (22 cases, 91.7%), cerebral atrophy (75%), and small, multifocal calcifications in the lentiform nuclei and deep cerebral white matter (54.2%). Homozygous mutations were identified in RNASEH2B (54.2%), RNASEH2A (20.8%), RNASEH2C (8.3%), SAMHD1 (8.3%), TREX1 (4.2%), and heterozygous mutations in IFIH1 (4.2%), with c.356A>G (p.Asp119Gly) in RNASEH2B being the most frequent mutation. Three novel mutations c.987delT and c.625 + 1G>A in SAMHD1 gene and c.961G>T in the IFIHI1 gene were identified.

CONCLUSIONS

This is the largest molecularly confirmed Aicardi-Goutières syndrome cohort from Arabia. By presenting these clinical and molecular findings, we hope to raise awareness of Aicardi-Goutières syndrome and to demonstrate the importance of specialist referral and molecular diagnosis.

Late diagnosis and atypical brain imaging of Aicardi-Goutières syndrome: are we failing to diagnose Aicardi-Goutières syndrome-2?

Aicardi-Goutières syndrome (AGS) is a rare disorder with in utero or postnatal onset of encephalopathy and progressive neurological deterioration. The seven genetic subtypes of AGS are associated with abnormal type I interferon-mediated innate immune response. Most patients with AGS present with progressive microcephaly, spasticity, and cognitive impairment. Some, especially those with type 2 (AGS2), manifest milder phenotypes, reduced childhood mortality, and relative preservation of physical and cognitive abilities. In this report, we describe two siblings (sister and brother) diagnosed with AGS2 in their second decade, who exhibited static encephalopathy since 1 year of age with spastic quadriplegia and anarthria but preserved intellect. Both were homozygous for the common pathogenic RNASEH2B allele (c.529G>A, p.Ala177Thr). Rather than manifesting calcifications and leukoencephalopathy, both had increased iron signal in the basal ganglia. Our report broadens the clinical and imaging spectrum of AGS2 and emphasizes the importance of including AGS2 in the differential diagnosis of idiopathic spastic cerebral palsy.

WHAT THIS PAPER ADDS

We identified two siblings (sister and brother) with atypical Aicardi-Goutières syndrome type 2 due to RNASEH2B mutation. Manifestations included spastic quadriplegia and anarthria but preserved intellect and increased iron signal in the basal ganglia. RNASEH2B-related Aicardi-Goutières syndrome type 2 can have present with a variable phenotype, including idiopathic spastic cerebral palsy.

Rare ADAR and RNASEH2B variants and a type I interferon signature in glioma and prostate carcinoma risk and tumorigenesis

In search of novel germline alterations predisposing to tumors, in particular to gliomas, we studied a family with two brothers affected by anaplastic gliomas, and their father and paternal great-uncle diagnosed with prostate carcinoma. In this family, whole-exome sequencing yielded rare, simultaneously heterozygous variants in the Aicardi-Goutières syndrome (AGS) genes ADAR and RNASEH2B co-segregating with the tumor phenotype. AGS is a genetically induced inflammatory disease particularly of the brain, which has not been associated with a consistently increased cancer risk to date. By targeted sequencing, we identified novel ADAR and RNASEH2B variants, and a 3- to 17-fold frequency increase of the AGS mutations ADAR,c.577C>G;p.(P193A) and RNASEH2B,c.529G>A;p.(A177T) in the germline of familial glioma patients as well as in test and validation cohorts of glioblastomas and prostate carcinomas versus ethnicity-matched controls, whereby rare RNASEH2B variants were significantly more frequent in familial glioma patients. Tumors with ADAR or RNASEH2B variants recapitulated features of AGS, such as calcification and increased type I interferon expression. Patients carrying ADAR or RNASEH2B variants showed upregulation of interferon-stimulated gene (ISG) transcripts in peripheral blood as seen in AGS. An increased ISG expression was also induced by ADAR and RNASEH2B variants in tumor cells and was blocked by the JAK inhibitor Ruxolitinib. Our data implicate rare variants in the AGS genes ADAR and RNASEH2B and a type I interferon signature in glioma and prostate carcinoma risk and tumorigenesis, consistent with a genetic basis underlying inflammation-driven malignant transformation in glioma and prostate carcinoma development.

Genetic, Phenotypic, and Interferon Biomarker Status in ADAR1-Related Neurological Disease

We investigated the genetic, phenotypic, and interferon status of 46 patients from 37 families with neurological disease due to mutations in ADAR1. The clinicoradiological phenotype encompassed a spectrum of Aicardi-Goutières syndrome, isolated bilateral striatal necrosis, spastic paraparesis with normal neuroimaging, a progressive spastic dystonic motor disorder, and adult-onset psychological difficulties with intracranial calcification. Homozygous missense mutations were recorded in five families. We observed a p.Pro193Ala variant in the heterozygous state in 22 of 23 families with compound heterozygous mutations. We also ascertained 11 cases from nine families with a p.Gly1007Arg dominant-negative mutation, which occurred de novo in four patients, and was inherited in three families in association with marked phenotypic variability. In 50 of 52 samples from 34 patients, we identified a marked upregulation of type I interferon-stimulated gene transcripts in peripheral blood, with a median interferon score of 16.99 (interquartile range [IQR]: 10.64-25.71) compared with controls (median: 0.93, IQR: 0.57-1.30). Thus, mutations in ADAR1 are associated with a variety of clinically distinct neurological phenotypes presenting from early infancy to adulthood, inherited either as an autosomal recessive or dominant trait. Testing for an interferon signature in blood represents a useful biomarker in this context.

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.