A young-onset frontal dementia with dramatic calcifications due to a novel CSF1R mutation

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.

Modeling CSF-1 receptor deficiency diseases - how close are we?

The role of colony-stimulating factor-1 receptor (CSF-1R) in macrophage and organismal development has been extensively studied in mouse. Within the last decade, mutations in the CSF1R have been shown to cause rare diseases of both pediatric (Brain Abnormalities, Neurodegeneration, and Dysosteosclerosis, OMIM #618476) and adult (CSF1R-related leukoencephalopathy, OMIM #221820) onset. Here we review the genetics, penetrance, and histopathological features of these diseases and discuss to what extent the animal models of Csf1r deficiency currently available provide systems in which to study the underlying mechanisms involved.

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.

The Role of White Matter Dysfunction and Leukoencephalopathy/Leukodystrophy Genes in the Aetiology of Frontotemporal Dementias: Implications for Novel Approaches to Therapeutics

Frontotemporal dementia (FTD) is a common cause of presenile dementia and is characterized by behavioural and/or language changes and progressive cognitive deficits. Genetics is an important component in the aetiology of FTD, with positive family history of dementia reported for 40% of cases. This review synthesizes current knowledge of the known major FTD genes, including C9orf72 (chromosome 9 open reading frame 72), MAPT (microtubule-associated protein tau) and GRN (granulin), and their impact on neuronal and glial pathology. Further, evidence for white matter dysfunction in the aetiology of FTD and the clinical, neuroimaging and genetic overlap between FTD and leukodystrophy/leukoencephalopathy are discussed. The review highlights the role of common variants and mutations in genes such as CSF1R (colony-stimulating factor 1 receptor), CYP27A1 (cytochrome P450 family 27 subfamily A member 1), TREM2 (triggering receptor expressed on myeloid cells 2) and TMEM106B (transmembrane protein 106B) that play an integral role in microglia and oligodendrocyte function. Finally, pharmacological and non-pharmacological approaches for enhancing remyelination are discussed in terms of future treatments of FTD.

A Novel Missense Mutation of the CSF1R Gene Causes Incurable CSF1R-Related Leukoencephalopathy: Case Report and Review of Literature

CSF1R-related leukoencephalopathy, mainly caused by the mutation of the colony stimulating factor 1 receptor (CSF1R) gene on chromosome 5, is an underestimated neurological disease typically presenting as early-onset cognitive decline and personality changes. Currently, there is no specific treatment for CSF1R-related leukoencephalopathy. Most clinicians failed to recognize this disease during an early disease stage, leading to a high rate of misdiagnosis. Although rare, an increasing amount of CSF1R-related leukoencephalopathy cases have been reported recently. In this study, we first report a 35-year-old woman with CSF1R-related leukoencephalopathy carrying a novel missense mutation c.2463G >C (p.W821C) of CSF1R. An extensive literature research was performed in order to better understand the broader genetic and clinical characteristics of CSF1R-related leukoencephalopathy. A total of 147 patients with CSF1R-related leukoencephalopathy confirmed either by the genetic test or brain biopsy were identified. Among them, 49 patients were sporadic, and the rest of individuals had a family history originating from 46 different families. Our study indicated that the average age of CSF1R-related leukoencephalopathy onset was 41.4 years. Typical clinical symptoms of CSF1R-related leukoencephalopathy include cognitive decline, movement disorders, behavior changes and mental disorders. Genetic studies have reported 93 missense mutations, 13 splicing mutations, 6 deletion/insertion mutations, 1 code shift mutation and 1 nonsense mutation of the CSF1R gene in patients with CSF1R-related leukoencephalopathy. Early genetic detection and brain biopsy would be helpful for a confirmed diagnosis, and more translational studies are needed to combat this devastating disease.

An Autopsy Proven Case of CSF1R-mutant Adult-onset Leukoencephalopathy with Axonal Spheroids and Pigmented Glia (ALSP) with Premature Ovarian Failure

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a progressive degenerative white matter disorder caused by mutations in the tyrosine kinase domain of the CSF1R gene. ALSP is often misdiagnosed as other diseases due to its rarity and various clinical presentations such as Parkinsonism, pyramidal signs, cognitive impairment and/or psychiatric symptoms. We describe an autopsy case of ALSP with a CSF1R mutation. A 61-year-old woman presented insidious-onset gait difficulty for 12 years since her age of 49, and premature ovarian failure since her age of 35. At initial hospital visit, brain magnetic resonance imaging revealed hydrocephalus. Initially, Parkinson's syndrome was diagnosed, and she was prescribed L-dopa/carbidopa because of spasticity and rigidity of extremities, which had worsened. Subsequently, severe neuropsychiatric symptoms and cognitive impairment developed and radiologically, features of leukoencephalopathy or leukodystrophy were detected. She showed a down-hill course and died, 12 years after initial diagnosis. At autopsy, the brain showed severe symmetric atrophy of bilateral white matter, paper-thin corpus callosum, thin internal capsule, and marked hydrocephalus. Microscopically, diffuse loss of white matter, relatively preserved subcortical U-fibers, and many eosinophilic bulbous neuroaxonal spheroids were noted, but there was no calcification. Pigmented glia with brown cytoplasmic pigmentation were readily found in the white matter, which were positive for Periodic acid-Schiff, p62, and CD163 stains, but almost negative for CD68. Whole-exome and Sanger sequencing revealed a CSF1R mutation (c.2539G>A, p.Glu847Lys) which was reported in prior one ALSP case. This example demonstrates that ALSP could be associated with premature ovarian failure.

CSF1R mutation presenting as dementia with Lewy bodies

Hereditary diffuse leukoencephalopathy with spheroids (HDLS) is an adult-onset autosomal dominant leukoencephalopathy resulting from mutations affecting the tyrosine kinase domain of the colony stimulating factor receptor 1 protein (encoded by CSF1R). The clinical phenotypes reported with CSF1R mutations are variable. We present a case of a patient with a pathogenic variant in the CSF1R gene with clinical and imaging features suggestive of Dementia with Lewy Bodies (DLB). This case expands the known clinical presentations associated with CSF1R mutations.

Recent advances in the genetics of frontotemporal dementia

Purpose of review

In this review we highlight recent advances in the human genetics of frontotemporal dementia (FTD). In addition to providing a broad survey of genes implicated in FTD in the last several years, we also discuss variation in genes implicated in both hereditary leukodystrophies and risk for FTD (e.g., TREM2, TMEM106B, CSF1R, AARS2, NOTCH3).

Recent findings

Over the past five years, genetic variation in approximately 50 genes has been confirmed or suggested to cause or influence risk for FTD and FTD-spectrum disorders. We first give background and discuss recent findings related to C9ORF72, GRN and MAPT, the genes most commonly implicated in FTD. We then provide a broad overview of other FTD-associated genes and go on to discuss new findings in FTD genetics in East Asian populations, including pathogenic variation in CHCHD10, which may represent a frequent cause of disease in Chinese populations. Finally, we consider recent insights gleaned from genome-wide association and genetic pleiotropy studies.

Summary

Recent genetic discoveries highlight cellular pathways involving autophagy, the endolysosomal system and neuroinflammation, and reveal an intriguing overlap between genes that confer risk for leukodystrophy and FTD.

CSF1R-related leukoencephalopathy: A major player in primary microgliopathies

Since the discovery of CSF1R gene mutations in families with hereditary diffuse leukoencephalopathy with spheroids in 2012, more than 70 different mutations have been identified around the world. Through the analyses of mutation carriers, CSF1R-related leukoencephalopathy has been distinctly characterized clinically, radiologically, and pathologically. Typically, patients present with frontotemporal dementia-like phenotype in their 40s-50s, accompanied by motor symptoms, including pyramidal and extrapyramidal signs. Women tend to develop the clinical symptoms at a younger age than men. On brain imaging, in addition to white matter abnormalities, thinning of the corpus callosum, diffusion-restricted lesions in the white matter, and brain calcifications are hallmarks. Primary axonopathy followed by demyelination was suggested by pathology. Haploinsufficiency of colony-stimulating factor-1 receptor (CSF1R) is evident in a patient with a frameshift mutation, facilitating the establishment of Csf1r haploinsufficient mouse model. These mice develop clinical, radiologic, and pathologic phenotypes consistent with those of human patients with CSF1R mutations. In vitro, perturbation of CSF1R signaling is shown in cultured cells expressing mutant CSF1R. However, the underlying mechanisms by which CSF1R mutations selectively lead to white matter degeneration remains to be elucidated. Given that CSF1R mainly expresses in microglia, CSF1R-related leukoencephalopathy is representative of primary microgliopathies, of which microglia have a pivotal and primary role in pathogenesis. In this review, we address the current knowledge of CSF1R-related leukoencephalopathy and discuss the putative pathophysiology, with a focus on microglia, as well as future research directions.

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP): Integrating the literature on hereditary diffuse leukoencephalopathy with spheroids (HDLS) and pigmentary orthochromatic leukodystrophy (POLD)

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a progressive degenerative white matter disorder. ALSP was previously recognized as two distinct entities, hereditary diffuse leukoencephalopathy with spheroids (HDLS) and pigmentary orthochromatic leukodystrophy (POLD). However, recent identification of mutations in the tyrosine kinase domain of the colony stimulating factor 1 receptor (CSF1R) gene, which regulates mononuclear cell lineages including microglia, have provided genetic and mechanistic evidence that POLD and HDLS should be regarded as a single clinicopathologic entity. We describe two illustrative cases of ALSP which presented with neuropsychiatric symptoms, progressive cognitive decline, and motor and gait disturbances. Antemortem diagnoses of autopsy-confirmed ALSP vary significantly, and include primary progressive multiple sclerosis, frontotemporal dementia, Alzheimer disease, atypical cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), corticobasal syndrome, and atypical Parkinson disease, suggesting that ALSP may be significantly underdiagnosed. This article presents a systematic review of ALSP in the context of two illustrative cases to help integrate the literature on HDLS and POLD. Consistent use of the term ALSP is suggested for clarity in the literature going forward.

CSF1R Mutation p.G589R and the Distribution Pattern of Brain Calcification

We herein report the case of a 47-year-old female with the colony-stimulating factor 1 receptor (CSF1R) mutation p.G589R, which is related to hereditary leukoencephalopathy with axonal spheroid (HDLS). The patient presented with an early-onset cognitive decline and progressive aphasia. Brain magnetic resonance imaging revealed HDLS-related alterations. In addition, brain computed tomography revealed interspersed spotty calcifications in the frontal and parietal subcortical white matter, while a characteristic "stepping stone" appearance was observed in the frontal pericallosal regions. Our findings emphasize the importance of calcification appearances in establishing an HDLS diagnosis and in screening for CSF1R mutations.