Diagnostic criteria for adult-onset leukoencephalopathy with axonal spheroids and pigmented glia due to CSF1R mutation

Clinical Diagnosis and Differential Diagnosis Between CSF1R- and AARS2-Related Leukoencephalopathy

CSF1R-related leukoencephalopathy (CSF1R-L) and AARS2-related leukoencephalopathy (AARS2-L) were two disease entities sharing similar phenotype and even pathological changes. Although clinically, radiologically, and pathologically similar, they were caused by mutation of two different genes. As the rarity of the two diseases, the differential diagnosis of them was difficult. 23 CSF1R-L and 6 AARS2-L patients were enrolled from the Leukoencephalopathy Clinic, Peking Union Medical College Hospital in China. Detailed clinical information, neuroimaging manifestations, and genetic data were collected and analyzed. Demographically, female patients were more in AARS2-L than CSF1R-L. Clinically, cognitive impairment and emotion/personality change were common in both groups. Bulbar palsy, extrapyramidal symptoms, and hemiplegia/pyramidal impairment were more common in CSF1R-L, while ataxia was significantly more common in AARS2-L. Abnormal menstruation including infertility was significantly more in AARS2-L. Radiologically, similar features were found, including lateral ventricle-centered white matter lesions, involving corpus callosum, avoiding U fibers. The lesions showed persistent hyperintensity on DWI image and were not contrasted after gadolinium enhancement. In CSF1R-L, the lesions could be widespread confluent or patchy and spotted, extending to centrum semiovale and subcortical white matter occasionally, which was significantly different from AARS2-L. Besides, brain stem lesion caused by pyramidal degeneration, spotted or linear calcification and obviously brain atrophy were common in CSF1R-L. In AARS2-L, periventricular white matter rarefaction was significantly common. No genotype and phenotype association was found in these two diseases. Although similar, there were several clinical and radiological features helping differentiating the two distinct diseases.

Clinical spectrum of adult-onset leukoencephalopathy with axonal spheroids and pigmented glia in individuals of Korean ancestry

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a rare white matter disease characterized by axonal and glial injury. Although its clinical characteristics have been described in case reports, the prevalence of CSF1R mutations in clinically suspected ALSP cases remains unclear. Herein, we analysed the frequency of CSF1R mutations in patients with probable or possible ALSP and describe the genetic, clinical, radiological, and pathological findings of ALSP cases in individuals of Korean ancestry. Twenty-eight patients with probable or possible ALSP diagnosed at Samsung Medical Center, Seoul, between January 2014 and August 2020, were retrospectively reviewed. All participants underwent brain magnetic resonance imaging (MRI) and CSF1R genetic testing. Overall, 9 of the 28 patients (32.1%) [5/6 (83.3%) of probable ALSP and 4/22 (18.2%) of possible ALSP] were confirmed to have pathogenic or likely pathogenic variants in CSF1R gene. Additionally, one patient without CSF1R mutation exhibited histopathological findings consistent with ALSP on brain biopsy. All patients with CSF1R mutation presented with cognitive impairment and/or psychiatric symptoms. Brain MRI revealed bilateral white matter hyperintensities in all patients, and 5/8 (62.5%) showed diffusion-restricted lesions. Notably, patients with CSF1R mutation had younger age at onset, rapidly progressive course, and diffuse hyperintensity in the splenium compared to patients without CSF1R mutation. Our findings suggest that for definite diagnosis, CSF1R genetic testing is recommended in patients who meet the diagnostic criteria for possible or probable ALSP. Our findings provide insights into the genetic, clinical, radiological, and pathological dimensions of ALSP in individuals of Korean ancestry.

Distinct patterns of white matter hyperintensity and cortical thickness of CSF1R-related leukoencephalopathy compared with subcortical ischemic vascular dementia

BACKGROUND

CSF1R-related leukoencephalopathy is a type of autosomal dominant leukodystrophy caused by mutations in the colony stimulating factor 1 receptor (CSF1R) gene. Subcortical ischemic vascular dementia (SIVaD), which is caused by cerebral small vessel disease, is similar to CSF1R-related leukoencephalopathy in that it mainly affects subcortical white matter. In this study, we compared the patterns of white matter hyperintensity (WMH) and cortical thickness in CSF1R-related leukoencephalopathy with those in SIVaD.

METHODS

Fourteen patients with CSF1R-related leukoencephalopathy and 129 with SIVaD were retrospectively recruited from three tertiary medical centers. We extracted and visualized WMH data using voxel-based morphometry to compare the WMH distributions between the two groups. Cortical thickness was measured using a surface-based method. Statistical maps of differences in cortical thickness between the two groups were generated using a surface model, with age, sex, education, and intracranial volume as covariates.

RESULTS

Predominant distribution of WMH in the CSF1R-related leukoencephalopathy group was in the bilateral frontal and parietal areas, whereas the SIVaD group showed diffuse WMH involvement in the bilateral frontal, parietal, and temporal areas. Compared with the SIVaD group, the CSF1R-related leukoencephalopathy group showed more severe corpus callosum atrophy (CCA) and widespread cortical thinning.

CONCLUSIONS

To our knowledge, this is the first study using the automated MR measurement to capture WMH, cortical thinning, and CCA with signal changes in CSF1R-related leukoencephalopathy. It provides new evidence regarding differences in the patterns of WMH distribution and cortical thinning between CSF1R-related leukoencephalopathy and SIVaD.

Mapping the journey of patients and care partners living with adult-onset leukoencephalopathy with axonal spheroids and pigmented glia: developing a framework for improvements in care

Aim: To identify and raise awareness of healthcare service gaps for individuals with adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP).Materials & methods: An ALSP patient journey map from symptom onset throughout disease course was developed using existing literature, patient and clinician feedback from a structured workshop and community survey data regarding attitudes toward genetic testing.Results: ALSP diagnosis is frequently delayed due to low awareness of this rare condition and symptom overlap with more common neurological conditions. Multiple factors impact patients' decision-making regarding genetic testing for ALSP, symptom management and participation in research studies.Conclusion: These results highlight the challenges faced by individuals with ALSP and should support program development to improve patient care.

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP): Estimation of pathological lesion stage from brain images

BACKGROUND

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a disease responsible for cognitive impairment in adult humans. It is caused by mutations in the colony stimulating factor 1 receptor gene (CSF1R) or alanyl-transfer (t) RNA synthetase 2 (AARS2) gene and affects brain white matter. Settlement of stages of the pathological brain lesions (Oyanagi et al. 2017) from the findings of brain imaging will be inevitably essential for prognostication.

METHODS

MRI images of eight patients with ALSP were analyzed semiquantitatively. White matter degeneration was assessed on a scale of 0 to 4 (none, patchy, large patchy, confluent, and diffuse) at six anatomical points, and brain atrophy on a scale 0 to 4 (none, slight, mild, moderate, and severe) in four anatomical areas. The scores of the two assessments were then summed to give total MRI scores of 0-40 points. Based on the scores, the MRI features were classified as Grades (0-4). Regression analysis was applied to mutual association between mRS, white matter degeneration score, brain atrophy score, the total MRI score and disease duration.

RESULTS

White matter degeneration score, brain atrophy score, and the total MRI score were significantly correlated with the disease duration. MRI Grades (2-4) based on the total MRI scores and the features of the images were well correlated with the pathological lesion stages (II - IV); i.e., 'large patchy' white matter degeneration in the frontal and parietal lobes (MRI Grade 2) corresponded to pathological Stage II, 'confluent' degeneration (Grade 3) to Stage III, and 'diffuse' degeneration (Grade 4) to Stage IV.

CONCLUSION

MRI Grades (2-4) resulted from the total MRI scores were well correlated with the pathological lesion Stages (II - IV).

Identification and characterization of a novel intronic splicing mutation in CSF1R-related leukoencephalopathy

AIMS

Colony stimulating factor 1 receptor (CSF1R)-related leukoencephalopathy is a rapidly progressing neurodegenerative disease caused by CSF1R gene mutations. This study aimed to identify and investigate the effect of a novel intronic mutation (c.1754-3C>G) of CSF1R on splicing.

METHODS

A novel intronic mutation was identified using whole-exome sequencing. To investigate the impact of this mutation, we employed various bioinformatics tools to analyze the transcription of the CSF1R gene and the three-dimensional structure of its encoded protein. Furthermore, reverse transcription polymerase chain reaction (RT-PCR) was performed to validate the findings.

RESULTS

A novel mutation (c.1754-3C>G) in CSF1R was identified, which results in exon 13 skipping due to the disruption of the 3' splice site consensus sequence NYAG/G. This exon skipping event was further validated in the peripheral blood of the mutation carrier through RT-PCR and Sanger sequencing. Protein structure prediction indicated a disruption in the tyrosine kinase domain, with the truncated protein showing significant structural alterations.

CONCLUSIONS

Our findings underscore the importance of intronic mis-splicing mutations in the diagnosis and management of CSF1R-related leukoencephalopathy.

Clinical presentation and diagnosis of adult-onset leukoencephalopathy with axonal spheroids and pigmented glia: a literature analysis of case studies

Introduction

Because adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a rare, rapidly progressive, debilitating, and ultimately fatal neurodegenerative disease, a rapid and accurate diagnosis is critical. This analysis examined the frequency of initial misdiagnosis of ALSP via comprehensive review of peer-reviewed published cases.

Methods

Data were extracted from a MEDLINE search via PubMed (January 1, 1980, through March 22, 2022) from eligible published case reports/series for patients with an ALSP diagnosis that had been confirmed by testing for the colony-stimulating factor-1 receptor gene (CSF1R) mutation. Patient demographics, clinical symptoms, brain imaging, and initial diagnosis data were summarized descriptively. Categorical data for patient demographics, symptoms, and brain imaging were stratified by initial diagnosis category to test for differences in initial diagnosis based on each variable.

Results

Data were extracted from a cohort of 291 patients with ALSP from 93 published case reports and case series. Mean (standard deviation) age of symptom onset was 43.2 (11.6) years. A family history of ALSP was observed in 59.1% of patients. Cognitive impairment (47.1%) and behavioral and psychiatric abnormalities (26.8%) were the most frequently reported initial symptoms. Of 291 total cases, an accurate initial diagnosis of ALSP was made in 72 cases (24.7%) and the most frequent initial misdiagnosis categories were frontotemporal dementia (28 [9.6%]) and multiple sclerosis (21 [7.2%]). Of the 219 cases (75.3%) that were initially mis- or undiagnosed, 206 cases (94.1%) were later confirmed as ALSP by immunohistology, imaging, and/or genetic testing; for the remaining 13 cases, no final diagnosis was reported. Initial diagnosis category varied based on age, family history, geographic region, mode of inheritance, and presenting symptoms of pyramidal or extrapyramidal motor dysfunction, behavioral and psychiatric abnormalities, cognitive impairment, and speech difficulty. Brain imaging abnormalities were common, and initial diagnosis category was significantly associated with white matter hyperintensities, white matter calcifications, and ventricular enlargement.

Discussion

In this literature analysis, ALSP was frequently misdiagnosed. Improving awareness of this condition and distinguishing it from other conditions with overlapping presenting symptoms is important for timely management of a rapidly progressive disease such as ALSP.

MRI pattern recognition in white matter disease

Magnetic resonance imaging (MRI) pattern recognition is a powerful tool for quick diagnosis of genetic and acquired white matter disorders. In many cases, distribution and character of white matter abnormalities directly point to a specific diagnosis and guide confirmatory testing. Knowledge of normal brain development is essential to interpret white matter changes in young children. MRI is also used for disease staging and treatment decisions in leukodystrophies and acquired disorders as multiple sclerosis, and as a biomarker to follow treatment effects.

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is an adult-onset, inherited white matter disorder encompassing two previously identified clinicopathologically similar entities: pigmentary orthochromatic leukodystrophy (POLD) and hereditary diffuse leukoencephalopathy with spheroids (HDLS). In this chapter, we discuss how advances in our genetic understanding of the condition have further delineated three distinct clinical entities within ALSP, namely CSF1R-related ALSP, AARS2-related leukoencephalopathy (AARS2-L), and AARS (HDLS-S). We provide descriptions of the clinical, radiologic, pathologic, and pathophysiologic findings in each entity, detailing their similarities and differences, and discuss current and future treatment options where available.

Adult-onset leukodystrophies: a practical guide, recent treatment updates, and future directions

Adult-onset leukodystrophies though individually rare are not uncommon. This group includes several disorders with isolated adult presentations, as well as several childhood leukodystrophies with attenuated phenotypes that present at a later age. Misdiagnoses often occur due to the clinical and radiological overlap with common acquired disorders such as infectious, immune, inflammatory, vascular, metabolic, and toxic etiologies. Increased prevalence of non-specific white matter changes in adult population poses challenges during diagnostic considerations. Clinico-radiological spectrum and molecular landscape of adult-onset leukodystrophies have not been completely elucidated at this time. Diagnostic approach is less well-standardized when compared to the childhood counterpart. Absence of family history and reduced penetrance in certain disorders frequently create a dilemma. Comprehensive evaluation and molecular confirmation when available helps in prognostication, early initiation of treatment in certain disorders, enrollment in clinical trials, and provides valuable information for the family for reproductive counseling. In this review article, we aimed to formulate an approach to adult-onset leukodystrophies that will be useful in routine practice, discuss common adult-onset leukodystrophies with usual and unusual presentations, neuroimaging findings, recent advances in treatment, acquired mimics, and provide an algorithm for comprehensive clinical, radiological, and genetic evaluation that will facilitate early diagnosis and consider active treatment options when available. A high index of suspicion, awareness of the clinico-radiological presentations, and comprehensive genetic evaluation are paramount because treatment options are available for several disorders when diagnosed early in the disease course.

Microglia and Brain Disorders: The Role of Vitamin D and Its Receptor

Accounting for 5-20% of the total glial cells present in the adult brain, microglia are involved in several functions: maintenance of the neural environment, response to injury and repair, immunesurveillance, cytokine secretion, regulation of phagocytosis, synaptic pruning, and sculpting postnatal neural circuits. Microglia contribute to some neurodevelopmental disorders, such as Nasu-Hakola disease (NHD), Tourette syndrome (TS), autism spectrum disorder (ASD), and schizophrenia. Moreover, microglial involvement in neurodegenerative diseases, such as Alzheimer's (AD) and Parkinson's (PD) diseases, has also been well established. During the last two decades, epidemiological and research studies have demonstrated the involvement of vitamin D3 (VD3) in the brain's pathophysiology. VD3 is a fat-soluble metabolite that is required for the proper regulation of many of the body's systems, as well as for normal human growth and development, and shows neurotrophic and neuroprotective actions and influences on neurotransmission and synaptic plasticity, playing a role in various neurological diseases. In order to better understand the exact mechanisms behind the diverse actions of VD3 in the brain, a large number of studies have been performed on isolated cells or tissues of the central nervous system (CNS). Here, we discuss the involvement of VD3 and microglia on neurodegeneration- and aging-related diseases.

Brain abnormalities, neurodegeneration, and dysosteosclerosis (BANDDOS): new cases, systematic literature review, and associations with CSF1R-ALSP

CSF1R mutations cause autosomal-dominant CSF1R-related leukoencephalopathy with axonal spheroids and pigmented glia (CSF1R-ALSP) and autosomal-recessive brain abnormalities, neurodegeneration, and dysosteosclerosis (BANDDOS). The former is increasingly recognized, and disease-modifying therapy was introduced; however, literature is scarce on the latter. This review analyzes BANDDOS and discusses similarities and differences with CSF1R-ALSP.We systematically retrieved and analyzed the clinical, genetic, radiological, and pathological data on the previously reported and our cases with BANDDOS. We identified 19 patients with BANDDOS (literature search according to the PRISMA 2020 guidelines: n = 16, our material: n = 3). We found 11 CSF1R mutations, including splicing (n = 3), missense (n = 3), nonsense (n = 2), and intronic (n = 2) variants and one inframe deletion. All mutations disrupted the tyrosine kinase domain or resulted in nonsense-mediated mRNA decay. The material is heterogenous, and the presented information refers to the number of patients with sufficient data on specific symptoms, results, or performed procedures. The first symptoms occurred in the perinatal period (n = 5), infancy (n = 2), childhood (n = 5), and adulthood (n = 1). Dysmorphic features were present in 7/17 cases. Neurological symptoms included speech disturbances (n = 13/15), cognitive decline (n = 12/14), spasticity/rigidity (n = 12/15), hyperactive tendon reflex (n = 11/14), pathological reflexes (n = 8/11), seizures (n = 9/16), dysphagia (n = 9/12), developmental delay (n = 7/14), infantile hypotonia (n = 3/11), and optic nerve atrophy (n = 2/7). Skeletal deformities were observed in 13/17 cases and fell within the dysosteosclerosis - Pyle disease spectrum. Brain abnormalities included white matter changes (n = 19/19), calcifications (n = 15/18), agenesis of corpus callosum (n = 12/16), ventriculomegaly (n = 13/19), Dandy-Walker complex (n = 7/19), and cortical abnormalities (n = 4/10). Three patients died in infancy, two in childhood, and one case at unspecified age. A single brain autopsy evidenced multiple brain anomalies, absence of corpus callosum, absence of microglia, severe white matter atrophy with axonal spheroids, gliosis, and numerous dystrophic calcifications.In conclusion, BANDDOS presents in the perinatal period or infancy and has a devastating course with congenital brain abnormalities, developmental delay, neurological deficits, osteopetrosis, and dysmorphic features. There is a significant overlap in the clinical, radiological, and neuropathological aspects between BANDDOS and CSF1R-ALSP. As both disorders are on the same continuum, there is a window of opportunity to apply available therapy in CSF1R-ALSP to BANDDOS.

Neuropsychological profile of CSF1R-related leukoencephalopathy

Introduction

The neuropsychological profile of CSF1R-related leukoencephalopathy (CRL) is undefined. This study defines the profile, contrasts it with that of other dementia syndromes, and highlights measures sensitive to cognitive impairment.

Methods

We administered a standardized battery of neuropsychological tests to five consecutive CRL cases.

Results

The neuropsychological profile of CRL reflects impaired general cognitive function, processing speed, executive function, speeded visual problem solving, verbal fluency, and self-reported depression and anxiety. Confrontation naming and memory are preserved. Within cognitive domains, certain measures more frequently identified impairment than others.

Discussion

CRL impairs general cognitive function, processing speed, executive function. Language and visual problem solving may be impaired if processing speed is required. Confrontation naming and memory are uniquely preserved, contrasting CRL to other dementia syndromes. Cognitive screens excluding processing speed and executive function may not detect CRL cognitive manifestations. Findings sharply define cognitive impairment of CRL and inform cognitive test selection.

Case report: Treatment of advanced CSF1-receptor associated leukoencephalopathy with hematopoietic stem cell transplant

CSF1 receptor-related leukoencephalopathy is a rare genetic disorder presenting with severe, adult-onset white matter dementia as one of the leading symptoms. Within the central nervous system, the affected CSF1-receptor is expressed exclusively in microglia cells. Growing evidence implicates that replacing the defective microglia with healthy donor cells through hematopoietic stem cell transplant might halt disease progression. Early initiation of that treatment is crucial to limit persistent disability. However, which patients are suitable for this treatment is not clear, and imaging biomarkers that specifically depict lasting structural damage are lacking. In this study, we report on two patients with CSF1R-related leukoencephalopathy in whom allogenic hematopoietic stem cell transplant at advanced disease stages led to clinical stabilization. We compare their disease course with that of two patients admitted in the same timeframe to our hospital, considered too late for treatment, and place our cases in context with the respective literature. We propose that the rate of clinical progression might be a suitable stratification measure for treatment amenability in patients. Furthermore, for the first time we evaluate [18F] florbetaben, a PET tracer known to bind to intact myelin, as a novel MRI-adjunct tool to image white matter damage in CSF1R-related leukoencephalopathy. In conclusion, our data add evidence for allogenic hematopoietic stem cell transplant as a promising treatment in CSF1R-related leukoencephalopathy patients with slow to moderate disease progression.

Primary microglia dysfunction or microgliopathy: A cause of dementias and other neurological or psychiatric disorders

Microglia are unique cells in the central nervous system (CNS), being considered a sub-type of CNS macrophage. These cells monitor nearby micro-regions, having roles that far exceed immunological and scavengering functions, being fundamental for developing, protecting and maintaining the integrity of grey and white matter. Microglia might become dysfunctional, causing abnormal CNS functioning early or late in the life of patients, leading to neurologic or psychiatric disorders and premature death in some patients. Observations that the impairment of normal microglia function per se could lead to neurological or psychiatric diseases have been mainly obtained from genetic and molecular studies of Nasu-Hakola disease, caused by TYROBP or TREM2 mutations, and from studies of adult-onset leukoencephalopathy with axonal spheroids (ALSP), caused by CSF1R mutations. These classical microgliopathies are being named here Microgliopathy Type I. Recently, mutations in TREM2 have also been associated with Alzheimer Disease. However, in Alzheimer Disease TREM2 allele variants lead to an impaired, but functional TREM2 protein, so that patients do not develop Nasu-Hakola disease but are at increased risk to develop other neurodegenerative diseases. Alzheimer Disease is the prototype of the neurodegenerative disorders associated with these TREM2 variants, named here the Microgliopathies Type II. Here, we review clinical, pathological and some molecular aspects of human diseases associated with primary microglia dysfunctions and briefly comment some possible therapeutic approaches to theses microgliopathies. We hope that our review might update the interesting discussion about the impact of intrinsic microglia dysfunctions in the genesis of some pathologic processes of the CNS.

Case Report: Novel CSF1R Variant in a Patient With Behavioral Variant Frontotemporal Dementia Syndrome With Prodromal Repetitive Scratching Behavior

CSF1R-related leukoencephalopathy is an autosomal dominant neurodegenerative disease caused by mutations in the tyrosine kinase domain of the colony stimulating factor 1 receptor (CSF1R). Several studies have found that hematogenic stem cell transplantation is an effective disease modifying therapy however the literature regarding prodromal and early symptoms CSF1R-related leukoencephalopathy is limited. We describe a 63-year-old patient with 4 years of repetitive scratching and skin picking behavior followed by 10 years of progressive behavioral, cognitive, and motor decline in a pattern suggesting behavioral variant of frontotemporal dementia. Brain MRI demonstrated prominent frontal and parietal atrophy accompanied by underlying bilateral patchy white matter hyperintensities sparing the U fibers and cavum septum pellucidum. Whole-exome sequencing revealed a novel, predicted deleterious missense variant in a highly conserved amino acid in the tyrosine kinase domain of CSF1R (p.Gly872Arg). Given this evidence and the characteristic clinical and radiological findings this novel variant was classified as likely pathogenic according to the American College of Medical Genetics standard guidelines. Detailed description of the prodromal scratching and skin picking behavior and possible underlying mechanisms in this case furthers knowledge about early manifestations of CSF1R-related leukoencephalopathy with the hope that early detection and timely administration of disease modifying therapies becomes possible.

Two Novel Intronic Mutations in the CSF1R Gene in Two Families With CSF1R-Microglial Encephalopathy

Objective: To describe two novel heterozygous splicing variants of the CSF1R gene responsible for CSF1R-microglial encephalopathy in two unrelated Han Chinese families and further explore the relationship between the pathological and neuroimaging findings in this disease.

Methods: The demographic data, detailed medical history, and clinical manifestations of two unrelated Han families with CSF1R-microglial encephalopathy were recorded. Some family members also underwent detailed neuropsychological evaluation, neuroimaging, and genetic testing. The probands underwent whole-exome sequencing (WES) or next-generation sequencing (NGS) to confirm the diagnosis. The findings were substantiated using Sanger sequencing, segregation analysis, and phenotypic reevaluation.

Results: Both families presented with a dominant hereditary pattern. Five of 27 individuals (four generations) from the first family, including the proband and his sister, father, uncle, and grandmother, presented with cognitive impairments clinically during their respective lifetimes. Brain magnetic resonance imaging (MRI) depicted symmetric, confluent, and diffuse deep white matter changes, atrophy of the frontoparietal lobes, and thinning of the corpus callosum. The proband’s brother remained asymptomatic; brain MRI revealed minimal white matter changes, but pseudo-continuous arterial spin labeling (pCASL) demonstrated a marked reduction in the cerebral blood flow (CBF) in the bilateral deep white matter and corpus callosum. Seven family members underwent WES, which identified a novel splice-site heterozygous mutation (c.2319+1C>A) in intron 20 of the CSF1R gene in four members. The proband from the second family presented with significant cognitive impairment and indifference; brain MRI depicted symmetric diffuse deep white matter changes and thinning of the corpus callosum. The proband’s mother reported herself to be asymptomatic, while neuropsychological evaluation suggested mild cognitive impairment, and brain MRI demonstrated abnormal signals in the bilateral deep white matter and corpus callosum. NGS of 55 genes related to hereditary leukodystrophy was performed for three members, which confirmed a novel splice-site heterozygous mutation (c.1858+5G>A) in intron 13 of the CSF1R gene in two members.

Conclusions: Our study identified two novel splicing mutation sites in the CSF1R gene within two independent Chinese families with CSF1R-microglial encephalopathy, broadening the genetic spectrum of CSF1R-microglial encephalopathy and emphasizing the value of pCASL for early detection of this disease.

Teaching case 1-2020 - ADDENDUM: Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia due to a novel CSF1R mutation - An unusual cause of dementia

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Four Swedish cases of CSF1R-related leukoencephalopathy: Visualization of clinical phenotypes

Colony stimulating factor 1 receptor (CSF1R)‐related leukoencephalopathy is a rare, genetic disease caused by heterozygous mutations in the CSF1R gene with rapidly progressive neurodegeneration, behavioral, cognitive, motor disturbances.

Altered intrinsic brain activity in patients with CSF1R-related leukoencephalopathy

CSF1R-related leukoencephalopathy is an adult-onset white matter disease with high disability and mortality, while little is known about its pathogenesis. This study introduced amplitude of low-frequency fluctuations (ALFF) and regional homogeneity (ReHo) based on resting-state functional magnetic resonance imaging(rsfMRI) to compare the spontaneous brain activities of patients and healthy controls, aiming to enhance our understanding of the disease. RsfMRI was performed on 16 patients and 23 healthy controls, and preprocessed for calculation of ALFF and ReHo. Permutation tests with threshold free cluster enhancement (TFCE) was applied for comparison (number of permutations = 5,000). The TFCE significance threshold was set at [Formula: see text] < 0.05. In addition, 10 was set as the minimum cluster size. Compared to healthy controls, the patient group showed decreased ALFF in right paracentral lobule, and increased ALFF in bilateral insula, hippocampus, thalamus, supramarginal and precentral gyrus, right inferior, middle and superior frontal gyrus, right superior and middle occipital gyrus, as well as left parahippocampal gyrus, fusiform, middle occipital gyrus and angular gyrus. ReHo was decreased in right supplementary motor area, paracentral lobule and precentral gyrus, while increased in right superior occipital gyrus and supramarginal gyrus, left parahippocampal gyrus, hippocampus, fusiform, middle occipital gyrus and angular gyrus, as well as bilateral middle occipital gyrus and midbrain. These results revealed altered spontaneous brain activities in CSF1R-related leukoencephalopathy, especially in limbic system and motor cortex, which may shed light on underlying mechanisms.

Neuroimaging phenotypes of CSF1R-related leukoencephalopathy: Systematic review, meta-analysis, and imaging recommendations

Colony-stimulating factor 1 receptor (CSF1R)-related leukoencephalopathy is a rare but fatal microgliopathy. The diagnosis is often delayed due to multifaceted symptoms that can mimic several other neurological disorders. Imaging provides diagnostic clues that help identify cases. The objective of this study was to integrate the literature on neuroimaging phenotypes of CSF1R-related leukoencephalopathy. A systematic review and meta-analysis were performed for neuroimaging findings of CSF1R-related leukoencephalopathy via PubMed, Web of Science, and Embase on 25 August 2021. The search included cases with confirmed CSF1R mutations reported under the previous terms hereditary diffuse leukoencephalopathy with spheroids, pigmentary orthochromatic leukodystrophy, and adult-onset leukoencephalopathy with axonal spheroids and pigmented glia. In 78 studies providing neuroimaging data, 195 cases were identified carrying CSF1R mutations in 14 exons and five introns. Women had a statistically significant earlier age of onset (p = 0.041, 40 vs 43 years). Mean delay between symptom onset and neuroimaging was 2.3 years. Main magnetic resonance imaging (MRI) findings were frontoparietal white matter lesions, callosal thinning, and foci of restricted diffusion. The hallmark computed tomography (CT) finding was white matter calcifications. Widespread cerebral hypometabolism and hypoperfusion were reported using positron emission tomography and single-photon emission computed tomography. In conclusion, CSF1R-related leukoencephalopathy is associated with progressive white matter lesions and brain atrophy that can resemble other neurodegenerative/-inflammatory disorders. However, long-lasting diffusion restriction and parenchymal calcifications are more specific findings that can aid the differential diagnosis. Native brain CT and brain MRI (with and without a contrast agent) are recommended with proposed protocols and pictorial examples are provided.

Adult-Onset Leukoencephalopathy With Axonal Spheroids and Pigmented Glia: Review of Clinical Manifestations as Foundations for Therapeutic Development

A comprehensive review of published literature was conducted to elucidate the genetics, neuropathology, imaging findings, prevalence, clinical course, diagnosis/clinical evaluation, potential biomarkers, and current and proposed treatments for adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), a rare, debilitating, and life-threatening neurodegenerative disorder for which disease-modifying therapies are not currently available. Details on potential efficacy endpoints for future interventional clinical trials in patients with ALSP and data related to the burden of the disease on patients and caregivers were also reviewed. The information in this position paper lays a foundation to establish an effective clinical rationale and address the clinical gaps for creation of a robust strategy to develop therapeutic agents for ALSP, as well as design future clinical trials, that have clinically meaningful and convergent endpoints.

Insights Into the Role of CSF1R in the Central Nervous System and Neurological Disorders

The colony-stimulating factor 1 receptor (CSF1R) is a key tyrosine kinase transmembrane receptor modulating microglial homeostasis, neurogenesis, and neuronal survival in the central nervous system (CNS). CSF1R, which can be proteolytically cleaved into a soluble ectodomain and an intracellular protein fragment, supports the survival of myeloid cells upon activation by two ligands, colony stimulating factor 1 and interleukin 34. CSF1R loss-of-function mutations are the major cause of adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) and its dysfunction has also been implicated in other neurodegenerative disorders including Alzheimer’s disease (AD). Here, we review the physiological functions of CSF1R in the CNS and its pathological effects in neurological disorders including ALSP, AD, frontotemporal dementia and multiple sclerosis. Understanding the pathophysiology of CSF1R is critical for developing targeted therapies for related neurological diseases.

Novel CSF1R variant in adult-onset leukoencephalopathy masquerading as frontotemporal dementia: a follow-up study

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a rare white matter degenerative disease manifesting as progressive cognitive decline, pyramidal, and extrapyramidal features resulting from mutations in the colony-stimulating factor-1 receptor (CSF1R) gene. We describe a sporadic case of a young man who developed five months history of progressive cognitive decline with predominant neuropsychiatric symptoms, suggestive of frontotemporal dementia. Brain magnetic resonance imaging (MRI) showed bilateral frontotemporal atrophy, high signal intensities in frontal and high parietal deep white matter with persistent diffusion restriction on follow-up imaging. Genetics showed a novel heterozygous mutation in CSF1R gene confirming the diagnosis of ALSP. Being a rare disease, and given its particular adult-onset presentation especially presenile cognitive impairment, it can pose a unique diagnostic challenge. The study highlights the importance of recognizing the disease early and broadens the clinical, genetic, and imaging spectrum of CSF1R gene mutation.

Clinical and genetic characterization of adult-onset leukoencephalopathy caused by CSF1R mutations

Objective

Mutations in the colony‐stimulating factor 1 receptor gene (CSF1R) were identified as a cause of adult‐onset inherited leukoencephalopathy. The present study aims at investigating the frequency, clinical characteristics, and functional effects of CSF1R mutations in Taiwanese patients with adult‐onset leukoencephalopathy.

Methods

Mutational analysis of CSF1R was performed in 149 unrelated individuals with leukoencephalopathy by a targeted resequencing panel covering the entire coding regions of CSF1R. In vitro analysis of the CSF1‐induced autophosphorylation activities of mutant CSF1R proteins was conducted to assess the pathogenicity of the CSF1R mutations.

Results

Among the eight CSF1R variants identified in this study, five mutations led to a loss of CSF1‐induced autophosphorylation of CSF1R proteins. Four mutations (p.K586*, p.G589R, p.R777Q, and p.R782C) located within the tyrosine kinase domain of CSF1R, whereas the p.T79M mutation resided in the immunoglobulin‐like domain. The five patients carrying the CSF1R mutations developed cognitive decline at age 41, 43, 50, 79, and 86 years, respectively. Psychiatric symptoms and behavior changes were observed in four of the five patients. The executive function and processing speed were severely impaired at an early stage, and their cognitive function deteriorated rapidly within 3–4 years. Diffusion‐restricted lesions at the subcortical regions and bilateral corticospinal tracts were found in three patients.

Interpretation

CSF1R mutations account for 3.5% (5/149) of the adult‐onset leukoencephalopathy in Taiwan. CSF1R mutations outside the tyrosine kinase domain may also disturb the CSF1R function and lead to the clinical phenotype. Molecular functional validation is important to determine the pathogenicity of novel CSF1R variants.

Evaluation of CSF1R-related adult onset leukoencephalopathy with axonal spheroids and pigmented glia diagnostic criteria

BACKGROUND AND PURPOSE

Diagnostic criteria for adult onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) due to colony-stimulating factor 1 receptor (CSF1R) mutation have recently been proposed. Our objective was to assess their accuracy in an independent multicenter cohort.

METHODS

We evaluated the sensitivity and specificity of the diagnostic criteria for ALSP (including the "probable" and "possible" definitions) in a national cohort of 22 patients with CSF1R mutation, and 59 patients with an alternative diagnosis of adult onset inherited leukoencephalopathy.

RESULTS

Overall, the sensitivity of the diagnostic criteria for ALSP was 82%, including nine of 22 patients diagnosed as probable and nine of 22 diagnosed as possible. Twenty of the 59 CSF1R mutation-negative leukoencephalopathies fulfilled the diagnostic criteria, leading to a specificity of 66%.

CONCLUSIONS

Diagnostic criteria for ALSP have an overall limited sensitivity along with a modest specificity. We suggest that in patients suspected of genetic leukoencephalopathy, a comprehensive magnetic resonance imaging pattern-based approach is warranted, together with white matter gene panel or whole exome sequencing.

Three novel mutations in Chinese patients with CSF1R-related leukoencephalopathy

Background

CSF1R-related encephalopathy refers to adult-onset leukodystrophy with neuroaxonal spheroids and pigmented glia (ALSP) due to CSF1R mutations, which is a rare autosomal dominant white matter disease including two pathological entities, hereditary diffuse leukoencephalopathy with spheroids (HDLS) and pigmentary orthochromatic leukodystrophy (POLD). The aim of this study was to identify additional causative mutations in the CSF1R gene and clarify their pathogenic effects.

Methods

Whole-exome sequencing was conducted for nine Chinese patients diagnosed with possible ALSP based on clinical and neuroimaging findings from March 2014 to June 2020 at Xuanwu Hospital (Beijing, China). Variant pathogenicity was assessed according to the American College of Medical Genetics and Genomics and Association for Molecular Pathology (ACMG/AMP) Standards and Guidelines.

Results

Mean ± standard deviation (range) age of disease onset in the nine patients was 39.22±9.63 [25-54] years. Four of the nine patients were male, and four out of nine had a remarkable family history. Seven CSF1R mutations were identified in the nine patients; four (p.G17C, p.R579Q, p.I794T and c.2909_2910insATCA) have been previously reported, while three (p.V613L, p.W821R and c.2442+2_2442+3dupT) were novel. Of the latter, two (p.V613L and p.W821R) were likely pathogenic and 1 (c.2442+2_2442+3dupT) was of uncertain significance according to ACMG/AMP criteria.

Conclusions

These findings expand the mutational spectrum of ALSP and provide a basis for future investigations on etiologic factors and potential management strategies for this disease.

Altered structural and functional connectivity in CSF1R-related leukoencephalopathy

CSF1R-related leukoencephalopathy is a rare white-matter encephalopathy characterized by motor and neuropsychiatric symptoms due to colony-stimulating factor 1 receptor (CSF1R) gene mutation. Few studies have investigated the intrinsic brain alternations of patients with CSF1R-related leukoencephalopathy. We aim to evaluate the structural and functional changes in those patients. Seven patients with CSF1R-related leukoencephalopathy and 15 age-matched healthy controls (HCs) underwent multimodal magnetic resonance imaging (MRI), including high-resolution T1-weighted imaging, T2-weighted fluid attenuated inversion recovery imaging, diffusion-weighted imaging, diffusion kurtosis imaging (DKI) and resting-state functional MRI. First, to detect structural alterations, the gray matter volumes were compared using voxel-based morphometry analyses. Second, DKI parametric maps were used to evaluate the white matter (WM) connectivity changes. Finally, we constructed a seed-based resting-state functional connectivity matrix based on 90 regions of interest and examined the functional network changes of CSF1R-related leukoencephalopathy. Unlike the HCs, patients with CSF1R-related leukoencephalopathy predominantly had morphological atrophy in the bilateral thalamus and left hippocampus. In addition, the abnormal diffusivity was mainly distributed in the splenium of the corpus callosum, periventricular regions, centrum semiovale, subcortical U-fibers and midline cortex structures. Moreover, the patients had significantly reduced functional connectivity between the bilateral caudate nucleus and their contralateral hippocampus. Therefore, in addition to hyperintensity on the T2-weighted images, CSF1R-related leukoencephalopathy also showed abnormal structural and functional alterations, including subcortical atrophy and reduced functional connectivity, as well as altered diffuse parameters in the WM and subcortical regions. These findings expand our understanding of the potential pathophysiologic mechanism behind this hereditary disease.

Diffusion-Weighted Imaging is Key to Diagnosing Specific Diseases

This article reviews diseases for which persistent signal abnormalities on diffusion-weighted imaging are the key to their diagnosis. Specifically, updated knowledge regarding the neuroimaging patterns of the following diseases is summarized: sporadic Creutzfeldt-Jakob disease, neuronal intranuclear inclusion disease, and hereditary diffuse leukoencephalopathy with axonal spheroids-colony-stimulating factor receptors/adult-onset leukoencephalopathy with axonal spheroids and pigmented glia. In addition, their differential diagnoses; clinical manifestations; and pathologic, genetic, and imaging correlates are discussed.

Dynamic analysis of CSF1R-related leukoencephalopathy on magnetic resonance imaging: a case report

Background

Colony-stimulating factor 1 receptor (CSF1R)-related leukoencephalopathy is a rare and rapidly progressive leukoencephalopathy characterized by cognitive, motor, and neuropsychiatric symptoms, which is often misdiagnosed. Magnetic resonance imaging (MRI) signs and follow-up MRI of CSF1R-related leukoencephalopathy could help in establishing a diagnosis, but these features are not widely known by general neurologists.

Case presentation

A 34-year-old man was admitted for progressive weakness of the right limbs over 8 months. His father and sister had a similar clinical evolution. The primary neurological signs were hemiplegia, cognitive decline, dysarthria, pyramidal signs, ataxia and parkinsonism, and rapid disease progression. Cerebrospinal fluid analysis results were normal. Despite receiving treatment for improving cerebral metabolism and relieving the muscle spasm, his symptoms did not improve significantly. Brain MRI showed lesions concentrated in the corpus callosum and the deep white matter of the bilateral parieto-occipital lobes, periventricular areas, and corticospinal tracts. There was an enhanced lesion after a gadolinium-enhanced MRI scan. Over the 8-month progression, the lesions always exhibited restricted diffusion. The diffuse lesions gradually increased as the disease progressed. Genetic sequencing results showed a novel heterozygous missense mutation (c.2267 T > C p.L756P) in the CSF1R gene. The patient was treated with citicoline and idebenone for 4 days to improve cerebral metabolism, but his symptoms did not improve significantly.

Conclusion

The multiple lesions involving the pyramidal tract and white matter showed continuously restricted diffusion on brain imaging and gradually increased with disease progression.

Pathologic basis of the preferential thinning of thecorpus callosum in adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP)

Background

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is an early onset dementia characterized by axonal loss in the cerebral white matter with swollen axons (spheroids). It had been reported that the preferential thinning and “focal lesions” of the corpus callosum were observed on T2-weighted MRI in ALSP patients. The present study aimed to reveal the pathologic basis of them in relation to brain lesion staging (I ~ IV: Oyanagi et al. 2017).

Methods

Seven autopsied brains of ALSP and five controls were neuropathologically examined.

Results

Even at Stage I, corpus callosum body showed evident atrophy, and the atrophy advanced with stage progression. Spheroid size and density were maximal at Stage II in both centrum semiovale and corpus callosum body, but spheroids were larger in corpus callosum body than in centrum semiovale. Microglia in the body at Stage II had a larger cytoplasm than those in centrum semiovale. But spheroids and microglia in the “focal lesions” were identical with those of centrum semiovale.

Conclusion

Preferential thinning of corpus callosum was considered to be formed in relation to peculiar morphological alteration of microglia there in ALSP. Instead, “focal lesions” were formed in connection with the lesions in centrum semiovale.

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Preferential thinning and “focal lesions” of corpus callosum in ALSP.

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Seven autopsied brains of ALSP and five controls were neuropathologically examined.

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Larger spheroids and more microglial alteration in corpus callosum than centrum semiovale.

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“Focal lesions” were formed in connection with the lesions in the centrum semiovale.

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Peculiar morphological change of microglia leads to the preferential thinning of corpus callosum.

Microglial replacement therapy: a potential therapeutic strategy for incurable CSF1R-related leukoencephalopathy

CSF1R-related leukoencephalopathy is an adult-onset leukoencephalopathy with axonal spheroids and pigmented glia caused by colony stimulating factor 1 receptor (CSF1R) gene mutations. The disease has a global distribution and currently has no cure. Individuals with CSF1R-related leukoencephalopathy variably present clinical symptoms including cognitive impairment, progressive neuropsychiatric and motor symptoms. CSF1R is predominantly expressed on microglia within the central nervous system (CNS), and thus CSF1R-related leukoencephalopathy is now classified as a CNS primary microgliopathy. This urgent unmet medical need could potentially be addressed by using microglia-based immunotherapies. With the rapid recent progress in the experimental microglial research field, the replacement of an empty microglial niche following microglial depletion through either conditional genetic approaches or pharmacological therapies (CSF1R inhibitors) is being studied. Furthermore, hematopoietic stem cell transplantation offers an emerging means of exchanging dysfunctional microglia with the aim of reducing brain lesions, relieving clinical symptoms and prolonging the life of patients with CSF1R-related leukoencephalopathy. This review article introduces recent advances in microglial biology and CSF1R-related leukoencephalopathy. Potential therapeutic strategies by replacing microglia in order to improve the quality of life of CSF1R-related leukoencephalopathy patients will be presented.

Adult-onset diffuse leukoencephalopathy with axonal spheroids and pigmented glia presenting with acute stroke-like symptoms: A rare clinical scenario

Adult-onset diffuse leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a rare progressive degenerative white matter disease caused by mutations in the colony-stimulating factor-1 receptor gene. Patients commonly present in the 4th or 5th decade with variable clinical presentations including behavioral changes, dementia, parkinsonism, and motor dysfunctions, eventually leading to death within a few years. Although the disease is typically hereditary, sporadic cases are known to occur. The classic MRI features of ALSP include T2 hyperintensities in the frontal and parietal white matter, scattered foci of restricted diffusion in the white matter, age-advanced cerebral involutional changes, thinning and signal changes in the corpus callosum, absence of infratentorial involvement and lack of enhancement. CT commonly shows tiny calcifications in the corpus callosum and deep white matter. We report a unique case of sporadic ALSP that initially presented as young stroke with acute onset of left-sided hemiparesis and no preceding history of cognitive decline. However, subsequent cognitive and behavioral changes lead to the consideration of an alternative diagnosis. Stroke-like symptoms is a very rare primary presentation of this disease entity. We have highlighted the classic MRI and CT features that helped to guide its diagnosis in our patient and prompted early corroborative genetic testing.

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia - An unusual cause of dementia

No abstract available.

[A case of hereditary diffuse leukoencephalopathy with spheroids and pigmented glia presenting with long-term mild psychiatric symptoms]

A 64-year-old woman visited our hospital with early-onset dementia and progressive gait disturbance. She had demonstrated a mild communication disorder at the age of ~40 years; however, her psychiatric symptoms at that time were mild and were not accompanied by social problems. At the age of 59, she presented with memory loss, visual hallucinations, and delusions. Over the following five years she developed gait difficulties that gradually deteriorated and suffered frequent falls. On admission, neurological examinations revealed severe pyramidal and extrapyramidal signs of akinetic mutism. MRI of the brain showed cerebral atrophy, enlarged lateral ventricles, thinning of the corpus callosum, and leukoencephalopathy in the frontal-parietal lobes. Additionally, CT revealed a small spotty calcification in the frontal subcortical white matter. Genetic analysis revealed a single-base substitution (c.2330G>A/p.R777Q) in exon 18 of the colony stimulating factor 1 receptor (CSF1R) gene, encoding the CSF1R protein. She was diagnosed with hereditary diffuse leukoencephalopathy with spheroids (HDLS). HDLS is included in the differential diagnosis of early-onset dementia and should be considered in patients with mild personality change and abnormal behavior in the early course of the illness.

Clinical features and genetic characteristics of hereditary diffuse leukoencephalopathy with spheroids due to CSF1R mutation: a case report and literature review

Background

Hereditary diffuse leukoencephalopathy with spheroid (HDLS) is an autosomal dominant white matter disease characterized by adult-onset cognitive impairment, behavioral or emotional changes, paresis, Parkinsonism, and seizures. Mutations in the gene encoding colony-stimulating factor 1 receptor (CSF1R) have been identified as the cause of HDLS.

Methods

Detail medical history, clinical features and brain imaging of a patient with adult-onset leukoencephalopathy, cognitive impairment and motor dysfunction was reviewed and next generation sequencing was performed. An extensive literature research was then performed to identify all patients with HDLS previously reported. The clinical characteristics, brain imaging and genetic features of patients with HDLS were reviewed.

Results

A novel CSF1R mutation, c.1952G>A p.G651E was identified in the patient. Extensive review showed that HDLS typically presents with broad phenotypic variability. The most common symptoms of HDLS were cognitive impairment, followed by psychiatric symptoms, Parkinsonism, gait disorder, and dysphagia. The most common brain imaging findings of HDLS were bilateral white matter lesion, mostly around the ventricles, frontal lobe, and parietal lobe. Calcifications in white matter on CT, cerebral atrophy and thinning of corpus callosum were also common features. Although HDLS demonstrates an autosomal dominant pattern, sporadic cases are not uncommon.

Conclusions

Early recognition of clinical and neuroradiographical characteristics of HDLS is key for the correct diagnosis of the disease.

A proposed synergistic effect of CSF1R and NMUR2 variants contributes to binge eating in hereditary diffuse leukoencephalopathy with spheroids

Background

The genetic mechanisms of binge eating (BE) as a disease identity remain obscure. BE is usually viewed as a part of the behavioral variant of frontotemporal dementia (bvFTD) features. We encountered a family with hereditary diffuse leukoencephalopathy with spheroids (HDLS) that manifested uniformly with binge-eating-onset dementia. The genetic factors associated with the rare phenotype were investigated.

Methods

The detailed phenotypes of the patients were described. We performed whole-exome sequencing (WES) of family members and repeat-primed PCR to analyze the patients' expansion size of C9orf72, a well-established gene causing FTD. The WES results of additional HDLS patients without BE manifestations were also investigated.

Results

All affected individuals had a BE-dementia-epilepsy pattern of disease progression. A recurrent disease-causing mutation in CSF1R established the diagnosis of HDLS in the family. No abnormalities in the expansion size of C9orf72 were detected. The concurrence of a recurrent CSF1R mutation and a rare variant in NMUR2, a gene functionally related to BE, was revealed in the affected family members. No potentially pathogenic variants in other known BE-associated genes were identified. Both the NMUR2 variant and the CSF1R mutation cosegregated with the BE-dementia-epilepsy phenotype in the family. In three additional HDLS patients without BE, no pathogenic variants in NMUR2 were detected.

Conclusions

We propose that synergistic genetic effects of NMUR2 and CSF1R variants may exist and contribute to the development of the BE phenotype in HDLS. NMUR2 is one of the potential susceptible genes in BE and may contribute in a background of a disrupted structural neuronetwork. Further studies in other BE-related disorders are required.

The influence of environment and origin on brain resident macrophages and implications for therapy

Microglia are the tissue-resident macrophages of the brain and spinal cord. They are critical players in the development, normal function, and decline of the CNS. Unlike traditional monocyte-derived macrophages, microglia originate from primitive hematopoiesis in the embryonic yolk sac and self-renew throughout life. Microglia also have a unique genetic signature among tissue resident macrophages. Recent studies identify the contributions of both brain environment and developmental history to the transcriptomic identity of microglia. Here we review this emerging literature and discuss the potential implications of origin on microglial function, with particular focus on existing and future therapies using bone-marrow- or stem-cell-derived cells for the treatment of neurological diseases.

Clinicopathologic characterization and abnormal autophagy of CSF1R-related leukoencephalopathy

Background

CSF1R-related leukoencephalopathy, also known as hereditary diffuse leukoencephalopathy with spheroids (HDLS), is a rare white-matter encephalopathy characterized by motor and neuropsychiatric symptoms due to colony-stimulating factor 1 receptor (CSF1R) gene mutation. Few of CSF1R mutations have been functionally testified and the pathogenesis remains unknown.

Methods

In order to investigate clinical and pathological characteristics of patients with CSF1R-related leukoencephalopathy and explore the potential impact of CSF1R mutations, we analyzed clinical manifestations of 15 patients from 10 unrelated families and performed brain biopsy in 2 cases. Next generation sequencing was conducted for 10 probands to confirm the diagnosis. Sanger sequencing, segregation analysis and phenotypic reevaluation were utilized to substantiate findings. Functional examination of identified mutations was further explored.

Results

Clinical and neuroimaging characteristics were summarized. The average age at onset was 35.9 ± 6.4 years (range 24–46 years old). Younger age of onset was observed in female than male (34.2 vs. 39.2 years). The most common initial symptoms were speech dysfunction, cognitive decline and parkinsonian symptoms. One patient also had marked peripheral neuropathy. Brain biopsy of two cases showed typical pathological changes, including myelin loss, axonal spheroids, phosphorylated neurofilament and activated macrophages. Electron microscopy disclosed increased mitochondrial vacuolation and disorganized neurofilaments in ballooned axons. A total of 7 pathogenic variants (4 novel, 3 documented) were identified with autophosphorylation deficiency, among which c.2342C > T remained partial function of autophosphorylation. Western blotting disclosed the significantly lower level of c.2026C > T (p.R676*) than wild type. The level of microtubule associated protein 1 light chain 3-II (LC3-II), a classical marker of autophagy, was significantly lower in mutants expressed cells than wild type group by western blotting and immunofluorescence staining.

Conclusions

Our findings support the loss-of-function and haploinsufficiency hypothesis in pathogenesis. Autophagy abnormality may play a role in the disease. Repairing or promoting the phosphorylation level of mutant CSF1R may shed light on therapeutic targets in the future. However, whether peripheral polyneuropathy potentially belongs to CSF1R-related spectrum deserves further study with longer follow-up and more patients enrolled.

Trial registration

ChiCTR, ChiCTR1800015295. Registered 21 March 2018.

Electronic supplementary material

The online version of this article (10.1186/s40035-019-0171-y) contains supplementary material, which is available to authorized users.

Factors predictive of the presence of a CSF1R mutation in patients with leukoencephalopathy

Background and purpose

The purpose was to identify statistically factors that correlate with the presence of a colony‐stimulating factor 1 receptor (CSF1R) mutation and to reevaluate the accuracy of the current diagnostic criteria for CSF1R‐related leukoencephalopathy.

Methods

CSF1R testing was conducted on 145 consecutive leukoencephalopathy cases who were clinically suspected of having adult‐onset leukoencephalopathy with axonal spheroids and pigmented glia. From these, 135 cases whose detailed clinical information was available were enrolled. Forward logistic stepwise regression was performed to generate a probability model to predict a positive CSF1R mutation result. The current diagnostic criteria were also applied to our cohort and their sensitivity and specificity were calculated.

Results

Twenty‐eight CSF1R‐mutation‐positive cases and 107 CSF1R‐mutation‐negative cases were identified. Our probability model suggested that factors raising the probability of a CSF1R‐mutation‐positive result were younger onset, parkinsonism, thinning of the corpus callosum and diffusion‐restricted lesions. It also showed that involuntary movements and brainstem or cerebellar atrophy were negative predictors of a CSF1R‐mutation‐positive result. In our cohort, the sensitivity and specificity for ‘probable’ or ‘possible’ CSF1R‐related leukoencephalopathy were 81% and 14%, respectively.

Conclusions

Clinical and brain imaging features predictive of the presence of a CSF1R mutation are proposed. Consideration of these factors will help prioritize patients for CSF1R testing.