Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL): A challenging diagnosis and a rare multiple sclerosis mimic.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is an extremely rare hereditary cerebral small vessel disease caused by homozygous or compound heterozygous mutations in the gene coding for high-temperature requirement A serine peptidase 1 (HtrA1). Given the rare nature of the disease, delays in diagnosis and misdiagnosis are not uncommon. In this article, we reported the first case of CARASIL from Saudi Arabia with a novel homozygous variant c.1156C>T in exon 7 of the HTRA1 gene. The patient was initially misdiagnosed with primary progressive multiple sclerosis and treated with rituximab. CARASIL should be considered in the differential diagnosis of patients with suspected atypical progressive multiple sclerosis who have additional signs such as premature scalp alopecia and low back pain with diffuse white matter lesions in brain MRI. Genetic testing is important to confirm the diagnosis.

One Disease with two Faces: Semidominant Inheritance of a Novel HTRA1 Mutation in a Consanguineous Family.

OBJECTIVES: To identify the underlying genetic defect for a consanguineous family with an unusually high number of members affected by cerebral small vessel disease. MATERIALS AND METHODS: A total of 6 individuals, of whom 3 are severely affected, from the family were clinically and radiologically evaluated. SNP genotyping was performed in multiple members to demonstrate genome-wide runs-of-homozygosity. Coding variants in the most likely candidate gene, HTRA1 were explored by Sanger sequencing. Published HTRA1-related phenotypes were extensively reviewed to explore the effect of number of affected alleles on phenotypic expression. RESULTS: Genome-wide homozygosity mapping identified a 3.2 Mbp stretch on chromosome 10q26.3 where HTRA1 gene is located. HTRA1 sequencing revealed an evolutionarily conserved novel homozygous c.824C>T (p.Pro275Leu) mutation, affecting the serine protease domain of HtrA1. Early-onset of cognitive and motor deterioration in homozygotes are in consensus with CARASIL. However, there was a clear phenotypic variability between homozygotes which includes alopecia, a suggested hallmark of CARASIL. All heterozygotes, presenting as CADASIL type 2, had spinal disk degeneration and several neuroimaging findings, including leukoencephalopathy and microhemorrhage despite a lack of severe clinical presentation. CONCLUSION: Here, we clearly demonstrate that CARASIL and CADASIL type 2 are two clinical consequences of the same disorder with different severities thorough the evaluation of the largest collection of homozygotes and heterozygotes segregating in a family. Considering the semi-dominant inheritance of HTRA1-related phenotypes, genetic testing and clinical follow-up must be offered for all members of a family with HTRA1 mutations regardless of symptoms.

Two Unique Mutations in HTRA1-Related Cerebral Small Vessel Disease in North America and Africa and Literature Review.

OBJECTIVE: To describe and compare two cases of North American and African patients who were diagnosed with HTRA1-related cerebral small vessel disease (CSVD) with homozygous and heterozygous mutations, respectively, in the linker domain of the HTRA1 gene. MATERIALS AND METHODS: Case reports and literature review. RESULTS: A 49-year-old man from Mexico presented with recurrent lacunar strokes and memory loss. A 46-year-old woman from Eritrea presented with progressive memory loss. Neither patient had alopecia. MRI of the brain and spine in both patients showed leukoencephalopathy, microbleeds and spondylosis. Microbleeds along the subpial surfaces of the brainstem were only seen in the Mexican man. Genetic sequencing of HTRA1 gene revealed a novel homozygous mutation of p.A173S in the Mexican man supporting cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). A heterozygous mutation of p.V175M was detected in the African woman, which has not been reported in patients of African ethnicity. In reviewing literature, CARASIL patients with mutation in the linker domain are older at neurological symptom onset and more frequently presented with stroke compared to patients with non-linker domain mutations. In patients of HTRA1-CSVD from heterozygous mutations, male is more common. CONCLUSIONS: HTRA1-related CSVD may be seen in patients of non-Asian ethnicity without alopecia. These case reports extend the clinical and radiographic spectrum of HTRA1-related CSVD.

HTRA1 expression profile and activity on TGF-ß signaling in HTRA1 mutation carriers.

High temperature requirement A1 (HTRA1) is a serine protease playing a modulatory role in various cell processes, particularly in the regulation of transforming growth factor-ß (TGF-ß) signaling. A deleterious role in late-onset cerebral small vessel diseases (CSVDs) of heterozygous HTRA1 mutations, otherwise causative in homozygosity of cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy, was recently suggested. However, the pathomechanism of these heterozygous mutations is still undefined. Our aim is to evaluate the expression profile and activity of HTRA1 on TGF-ß signaling in fibroblasts from four subjects carrying the HTRA1 heterozygous mutations-p.E42Dfs*173, p.A321T, p.G295R, and p.Q151K. We found a 50% reduction of HTRA1 expression in HTRA1 mutation carriers compared to the control. Moreover, we showed no changes in TGF-ß signaling pathway downstream intermediate, Phospho Smad2/3. However, we found overexpression of genes involved in the extracellular matrix formation in two heterozygous HTRA1 carriers. Our results suggest that each heterozygous HTRA1 missense mutation displays a different and peculiar HTRA1 expression pattern and that CSVD phenotype may also result from 50% of HTRA1 expression.

Monogenic cerebral small-vessel diseases: diagnosis and therapy. Consensus recommendations of the European Academy of Neurology.

BACKGROUND AND PURPOSE: Guidelines on monogenic cerebral small-vessel disease (cSVD) diagnosis and management are lacking. Endorsed by the Stroke and Neurogenetics Panels of the European Academy of Neurology, a group of experts has provided recommendations on selected monogenic cSVDs, i.e. cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), autosomal dominant High Temperature Requirement A Serine Peptidase 1 (HTRA1), cathepsin-A-related arteriopathy with strokes and leukoencephalopathy (CARASAL), pontine autosomal dominant microangiopathy and leukoencephalopathy (PADMAL), Fabry disease, mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and type IV collagen (COL4)A1/2. METHODS: We followed the Delphi methodology to provide recommendations on several unanswered questions related to monogenic cSVD, including genetic testing, clinical and neuroradiological diagnosis, and management. RESULTS: We have proposed 'red-flag' features suggestive of a monogenic disease. General principles applying to the management of all cSVDs and specific recommendations for the individual forms of monogenic cSVD were agreed by consensus. CONCLUSIONS: The results provide a framework for clinicians involved in the diagnosis and management of monogenic cSVD. Further multicentre observational and treatment studies are still needed to increase the level of evidence supporting our recommendations.

Establishment and identification of a novel HTRA1 mutation mice model.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathyis a rare form of inherited cerebral small vessel disease associated with mutations in the high-temperature requirement serine peptidase A1 gene. As of now, only about 50 cases have been reported. In 2012, our group reported a family with a novel mutant of the high-temperature requirement serine peptidase A1 gene in China for the first time. To further explore the molecular pathogenesis of cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy, a recombination mouse model expressed human high-temperature requirement serine peptidase A1 gene mutant identified by our group was generated using the Donor & Clustered Regularly Interspaced Short Palindromic Repeats/Cas9 system and termed the Mut-high-temperature requirement serine peptidase A1 geneL364P mouse model. Results show that Mut-high-temperature requirement serine peptidase A1 geneL364P mice present similar pathological characteristics to patients with cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy, suggesting that the Mut-high-temperature requirement serine peptidase A1 geneL364P mouse model was generated successfully. Moreover, apoptosis was induced in mouse brain vascular smooth muscle cells derived from Mut-high-temperature requirement serine peptidase A1 geneL364P mice. In summary, the cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy mouse model described in this study will be beneficial to demonstrate the pathological mechanism of cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy and provide new therapeutic targets for clinical treatment.

A Case of Leukoencephalopathy and Small Vessels Disease Caused by a Novel HTRA1 Homozygous Mutation.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a heritable, rare small vessel disease, which is caused by HTRA1 mutations and mostly reported Japanese and Chinese population. CARASIL is an orphan disease, which presents with progressive motor and cognitive impairment, alopecia, and spondylosis. The disease typically starts with lumbago at early twenties. Ischemic strokes start at mid-twenties. Patients have no cardiovascular or any other risk factors. Multiple lacunar infarcts and leukoencephalopathy cause progressive neurologic involvement. Leukoencephalopathy and small vessel disease without any risk factors is a significant finding for the differential diagnosis of HTRA1 gene pathology. This report presents clinical and genetic features of a rare case of typical CARASIL from Turkey who was followed with uncertain diagnoses for years.

Genetic Factors of Cerebral Small Vessel Disease and Their Potential Clinical Outcome.

Cerebral small vessel diseases (SVD) have been causally correlated with ischemic strokes, leading to cognitive decline and vascular dementia. Neuroimaging and molecular genetic tests could improve diagnostic accuracy in patients with potential SVD. Several types of monogenic, hereditary cerebral SVD have been identified: cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), cathepsin A-related arteriopathy with strokes and leukoencephalopathy (CARASAL), hereditary diffuse leukoencephalopathy with spheroids (HDLS), COL4A1/2-related disorders, and Fabry disease. These disorders can be distinguished based on their genetics, pathological and imaging findings, clinical manifestation, and diagnosis. Genetic studies of sporadic cerebral SVD have demonstrated a high degree of heritability, particularly among patients with young-onset stroke. Common genetic variants in monogenic disease may contribute to pathological progress in several cerebral SVD subtypes, revealing distinct genetic mechanisms in different subtype of SVD. Hence, genetic molecular analysis should be used as the final gold standard of diagnosis. The purpose of this review was to summarize the recent discoveries made surrounding the genetics of cerebral SVD and their clinical significance, to provide new insights into the pathogenesis of cerebral SVD, and to highlight the possible convergence of disease mechanisms in monogenic and sporadic cerebral SVD.

Review: Vascular dementia: clinicopathologic and genetic considerations.

The incidence and severity of cerebrovascular disease (CVD) increase with advancing age, as does the risk of developing Alzheimer's disease (AD). Not surprisingly, heterogeneous forms of CVD may coexist with AD changes in the 'ageing brain'. These include angiopathies (affecting both large and small arteries) that result from 'classical' risk factors (hypertension, smoking and diabetes) and others (cerebral amyloid angiopathy) that are biochemically closely linked to AD. The morphologic consequences of these various vascular diseases are infarcts and/or haemorrhages of varying sizes within the brain, which lead to neurocognitive decline that may mimic AD - though the vascular abnormalities are usually detectable by neuroimaging. More subtle effects of CVD may include neuroinflammation and biochemical 'lesions' that have no reliable morphologic correlate and thus escape the attention of even an experienced Neuropathologist. The pathogenesis of hippocampal injury resembling ischaemic change - commonly seen in the brains of geriatric subjects - remains controversial. In recent years, genetically determined forms of microangiopathy (e.g. CADASIL, CARASIL, Trex1-related microangiopathies, CARASAL, familial forms of cerebral amyloid angiopathy or CAA) have provided interesting cellular and molecular clues to the pathogenesis of sporadic microvascular disease such as arteriolosclerosis and AD-related CAA.

CADASIL brain vessels show a HTRA1 loss-of-function profile.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and a phenotypically similar recessive condition (CARASIL) have emerged as important genetic model diseases for studying the molecular pathomechanisms of cerebral small vessel disease (SVD). CADASIL, the most frequent and intensely explored monogenic SVD, is characterized by a severe pathology in the cerebral vasculature including the mutation-induced aggregation of the Notch3 extracellular domain (Notch3ECD) and the formation of protein deposits of insufficiently determined composition in vessel walls. To identify key molecules and pathways involved in this process, we quantitatively determined the brain vessel proteome from CADASIL patient and control autopsy samples (n = 6 for each group), obtaining 95 proteins with significantly increased abundance. Intriguingly, high-temperature requirement protein A1 (HTRA1), the extracellular protease mutated in CARASIL, was found to be strongly enriched (4.9-fold, p = 1.6 × 10-3) and to colocalize with Notch3ECD deposits in patient vessels suggesting a sequestration process. Furthermore, the presence of increased levels of several HTRA1 substrates in the CADASIL proteome was compatible with their reduced degradation as consequence of a loss of HTRA1 activity. Indeed, a comparison with the brain vessel proteome of HTRA1 knockout mice (n = 5) revealed a highly significant overlap of 18 enriched proteins (p = 2.2 × 10-16), primarily representing secreted and extracellular matrix factors. Several of them were shown to be processed by HTRA1 in an in vitro proteolysis assay identifying them as novel substrates. Our study provides evidence for a loss of HTRA1 function as a critical step in the development of CADASIL pathology linking the molecular mechanisms of two distinct SVD forms.

The pathobiology of vascular malformations: insights from human and model organism genetics.

Vascular malformations may arise in any of the vascular beds present in the human body. These lesions vary in location, type, and clinical severity of the phenotype. In recent years, the genetic basis of several vascular malformations has been elucidated. This review will consider how the identification of the genetic factors contributing to different vascular malformations, with subsequent functional studies in animal models, has provided a better understanding of these factors that maintain vascular integrity in vascular beds, as well as their role in the pathogenesis of vascular malformations. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Histopathologic features of an autopsied patient with cerebral small vessel disease and a heterozygous HTRA1 mutation.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a hereditary cerebral small vessel disease (CSVD) caused by homozygous or compound heterozygous mutations of the high temperature requirement A serine peptidase 1 gene (HTRA1). Affected patients suffer from cognitive impairment, recurrent strokes, lumbago and alopecia. Recently, clinical studies have indicated that some patients with heterozygous mutations in HTRA1 may also suffer CSVD. Here, we report the histopathologic features of an autopsied 55-year-old male patient who had shown cognitive impairment and multiple cerebral infarcts, and was found to have a heterozygous missense mutation (p.R302Q) in the HTRA1 gene. Histologically, small vessels in the brain and spinal cord showed intimal proliferation, splitting of the internal elastic lamina, and degeneration of smooth muscle cells in the tunica media. Thus, although less severe, the features were quite similar to those of patients with CARASIL, indicating that patients with heterozygous mutations develop CSVD through underlying pathomechanisms similar to those of CARASIL.

A Chinese CARASIL Patient Caused by Novel Compound Heterozygous Mutations in HTRA1.

Our objective is to reported a Chinese CARASIL patient caused by novel compound heterozygous mutations in HTRA1. Detailed clinical and neuroimaging examination were conducted in proband and her available family members. Sanger sequencing of NOTCH3 and HTRA1 was used to investigate causative mutations. The patient was born in an outbred family. She experienced recurrent transient ischemic attacks, hair loss, and low back pain. Brain magnetic resonance imaging showed multiple lacunar infarctions, diffuse leukoencephalopathy, and multiple microbleeds of white matter. A compound heterozygous mutation, c.958G > A (p.D320N) and c.1021G > A (p.G341J), were identified in the proband. This report highlights that screening of HTRA1 should be considered in young SVD patient despite from outbred families.

A CARASIL Patient from Americas with Novel Mutation and Atypical Features: Case Presentation and Literature Review.

OBJECTIVE: Reporting a novel mutation in the HTRA1 gene in a CARASIL patient from Americas. METHODS: Clinical presentation and neuroimaging were consistent with CARASIL. HTRA1 DNA sequencing was performed using advanced ("next generation") sequencing technology. The results revealed a homozygous missense mutation as c.616G>A (p.Gly206Arg) in the HTRA1 gene. RESULTS: A 24-year-old man with a history of chronic back pain presented with recurrent ischemic strokes. A diagnosis of CARASIL was made with the finding of a novel homozygous missense mutation c.616G>A in HTRA1 gene, resulting in change from Glycine to Arginine in the Serine Protease HTRA1. Brain imaging showed multiple lacunar infarcts with extensive abnormalities of the white matter that spared the external capsules. He also had unilateral decreased hearing with craniofacial asymmetry. None of the above features have been previously described in known CARASIL patients. Both parents of the proband were heterozygous for the same missense mutation. CONCLUSION: We discovered a novel missense mutation (c.616G>A) associated with a phenotype of CARASIL. This is the first genetically backed case of CARASIL in the new world. The patient's craniofacial abnormalities, including asymmetry of the head, may be related to impaired modulation of transforming growth factor-ß1, the result of loss of proteolytic activity of HTRA1. External capsules remained unaffected, despite findings of advanced changes in the rest of the cerebral white matter. Literature is briefly reviewed. The patient's history, neurological exam, neuroimaging, and genetic testing are included.

Heterozygous HTRA1 mutations are associated with autosomal dominant cerebral small vessel disease.

Cerebral small vessel disease represents a heterogeneous group of disorders leading to stroke and cognitive impairment. While most small vessel diseases appear sporadic and related to age and hypertension, several early-onset monogenic forms have also been reported. However, only a minority of patients with familial small vessel disease carry mutations in one of known small vessel disease genes. We used whole exome sequencing to identify candidate genes in an autosomal dominant small vessel disease family in which known small vessel disease genes had been excluded, and subsequently screened all candidate genes in 201 unrelated probands with a familial small vessel disease of unknown aetiology, using high throughput multiplex polymerase chain reaction and next generation sequencing. A heterozygous HTRA1 variant (R166L), absent from 1000 Genomes and Exome Variant Server databases and predicted to be deleterious by in silico tools, was identified in all affected members of the index family. Ten probands of 201 additional unrelated and affected probands (4.97%) harboured a heterozygous HTRA1 mutation predicted to be damaging. There was a highly significant difference in the number of likely deleterious variants in cases compared to controls (P = 4.2 × 10(-6); odds ratio = 15.4; 95% confidence interval = 4.9-45.5), strongly suggesting causality. Seven of these variants were located within or close to the HTRA1 protease domain, three were in the N-terminal domain of unknown function and one in the C-terminal PDZ domain. In vitro activity analysis of HTRA1 mutants demonstrated a loss of function effect. Clinical features of this autosomal dominant small vessel disease differ from those of CARASIL and CADASIL by a later age of onset and the absence of the typical extraneurological features of CARASIL. They are similar to those of sporadic small vessel disease, except for their familial nature. Our data demonstrate that heterozygous HTRA1 mutations are an important cause of familial small vessel disease, and that screening of HTRA1 should be considered in all patients with a hereditary small vessel disease of unknown aetiology.

Shifting the CARASIL paradigm: report of a non-Asian family and literature review.

BACKGROUND AND PURPOSE: Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a rare form of nonhypertensive cerebral small-vessel disease caused by mutations in the HTRA1 gene. CARASIL is characterized by early adulthood onset of subcortical infarcts, cognitive impairment, alopecia, and spondylosis. Until recently, this disorder was almost exclusively reported in the Asian population. METHODS: Description of the clinical, imaging, and genetic study of 2 siblings with CARASIL, with a brief comparative review of published non-Asian cases of the disease. RESULTS: Both patients exhibited the typical phenotype: cerebral small-vessel disease, spondylosis, and abnormal hair lost. Mutation screening was performed for NOTCH3 and HTRA1 genes. No mutations were found in NOTCH3. The study revealed the presence of a homozygous c.496C>T substitution in HTRA1 in both siblings. CONCLUSION: This report highlights the need of considering this entity in the differential diagnosis of cerebral small-vessel disease in young patients, even in the non-Asian populations.

A human induced pluripotent stem cell model from a patient with hereditary cerebral small vessel disease carrying a heterozygous R302Q mutation in HTRA1.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is an inherited cerebral small vessel disease (CSVD) caused by biallelic mutations in the high-temperature requirement serine peptidase A1 (HTRA1) gene. Even heterozygous mutations in HTRA1 are recently revealed to cause cardinal clinical features of CSVD. Here, we report the first establishment of a human induced pluripotent stem cell (hiPSC) line from a patient with heterozygous HTRA1-related CSVD. Peripheral blood mononuclear cells (PBMCs) were reprogrammed by the transfection of episomal vectors encoding human OCT3/4 (POU5F1), SOX2, KLF4, L-MYC, LIN28, and a murine dominant-negative mutant of p53 (mp53DD). The established iPSCs had normal morphology as human pluripotent stem cells and normal karyotype (46XX). Moreover, we found that the HTRA1 missense mutation (c.905G>A, p.R302Q) was heterozygous. These iPSCs expressed pluripotency-related markers and had the potential to differentiate into all three germ layers in vitro. HTRA1 and the supposed disease-associated gene NOG were differentially expressed in the patient iPSCs at mRNA levels compared to those of control lines. The iPSC line would facilitate in vitro research for understanding the cellular pathomechanisms caused by the HTRA1 mutation including its dominant-negative effect.

The emerging role of the HTRA1 protease in brain microvascular disease.

Pathologies of the brain microvasculature, often referred to as cerebral small-vessel disease, are important contributors to vascular dementia, the second most common form of dementia in aging societies. In addition to their role in acute ischemic and hemorrhagic stroke, they have emerged as major cause of age-related cognitive decline in asymptomatic individuals. A central histological finding in these pathologies is the disruption of the vessel architecture including thickening of the vessel wall, narrowing of the vessel lumen and massive expansion of the mural extracellular matrix. The underlying molecular mechanisms are largely unknown, but from the investigation of several disease forms with defined etiology, high temperature requirement protein A1 (HTRA1), a secreted serine protease degrading primarily matrisomal substrates, has emerged as critical factor and potential therapeutic target. A genetically induced loss of HTRA1 function in humans is associated with cerebral autosomal-recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), a rare, hereditary form of brain microvascular disease. Recently, proteomic studies on cerebral amyloid angiopathy (CAA), a common cause of age-related dementia, and cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), the most prevalent monogenic small-vessel disease, have provided evidence for an impairment of HTRA1 activity through sequestration into pathological protein deposits, suggesting an alternative mechanism of HTRA1 inactivation and expanding the range of diseases with HTRA1 involvement. Further investigations of the mechanisms of HTRA1 regulation in the brain microvasculature might spawn novel strategies for the treatment of small-vessel pathologies.

Patients with heterozygous HTRA1-related cerebral small vessel disease misdiagnosed with other diseases: Two case reports.

White matter hyperintensities (WMHs) on brain magnetic resonance (MR) images are characteristic of hereditary cerebral small vessel disease (CSVD), including high-temperature requirement serine peptidase A1 (HTRA1)-related CSVD. Although HTRA1-related CSVD is increasingly recognized, the diagnosis is still challenging. We encountered two patients with HTRA1-related CSVD who were misdiagnosed with other diseases, including multiple sclerosis and idiopathic normal-pressure hydrocephalus. Both patients had extended WMHs in addition to multiple lacunes and microbleeds on brain MR images, which are characteristic of CSVD. If lacunes or microbleeds are found in patients with severe WMHs, genetic tests for hereditary CSVD should be considered.

Identified novel heterozygous HTRA1 pathogenic variants in Chinese patients with HTRA1-associated dominant cerebral small vessel disease.

Background: Homozygous and compound heterozygous mutations in HTRA1 cause cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). Recently, heterozygous pathogenic variants in HTRA1 were described in patients with autosomal dominant cerebral small vessel disease (CSVD). Here, we investigated the genetic variants in a cohort of Chinese patients with CSVD. Methods: A total of 95 Chinese index patients with typical characteristics of CSVD were collected. Whole exome sequencing was performed in the probands, followed by Sanger sequencing. Pathogenicity prediction software was applied to evaluate the pathogenicity of the identified variants. Results: We detected five heterozygous HTRA1 pathogenic variants in five index patients. These pathogenic variants included four known variants (c.543delT, c.854C>T, c.889G>A, and c.824C>T) and one novel variant (c.472 + 1G>A). Among them, c.854C>T, c.824C>T, and c.472 + 1G>A have never been reported in China and c.889G>A was once reported in homozygous but never in heterozygous. Three of them were distributed in exon 4, one in exon 2, and another splicing variant in intron 1. Four out of five probands presented typical features of CARASIL but less severe. The common clinical features included lacunar infarction, cognitive decline, alopecia, and spondylosis. All of them showed leukoencephalopathy, and the main involved cerebral area include periventricular and frontal area, centrum semiovale, thalamus, and corpus callosum. Anterior temporal lobes and external capsule involvement were also observed. Three probands had intracranial microbleeds. Conclusion: Our study expanded the mutation spectrum of HTRA1, especially in Chinese populations, and provided further evidence for "hot regions" in exon 1-4, especially in exon 4, in heterozygous HTRA1 pathogenic variants. Our work further supported that patients with heterozygous HTRA1 pathogenic variants presented with similar but less-severe features than CARASIL but in an autosomal dominantly inherited pattern.