Small vessel disease in primary familial brain calcification with novel truncating PDGFB variants.

INTRODUCTION: Primary familial brain calcification (PFBC) is a neurodegenerative disease characterised by bilateral calcification in the brain, especially in the basal ganglia, leading to neurological and neuropsychiatric manifestations. White matter hyperintensities (WMH) have been described in patients with PFBC and pathogenic variants in the gene for platelet-derived growth factor beta polypeptide (PDGFB), suggesting a manifest cerebrovascular process. We present below the cases of two PFBC families with PDGFB variants and stroke or transient ischaemic attack (TIA) episodes. We examine the possible correlation between PFBC and vascular events as stroke/TIA, and evaluate whether signs for vascular disease in this condition are systemic or limited to the cerebral vessels. MATERIAL AND METHODS: Two Swedish families with novel truncating PDGFB variants, p.Gln140* and p.Arg191*, are described clinically and radiologically. Subcutaneous capillary vessels in affected and unaffected family members were examined by light and electron microscopy. RESULTS: All mutation carriers showed WMH and bilateral brain calcifications. The clinical presentations differed, with movement disorder symptoms dominating in family A, and psychiatric symptoms in family B. However, affected members of both families had stroke, TIA, and/or asymptomatic intracerebral ischaemic lesions. Only one of the patients had classical vascular risk factors. Skin microvasculature was normal. CONCLUSIONS: Patients with these PDGFB variants develop microvascular changes in the brain, but not the skin. PDGFB-related small vessel disease can manifest radiologically as cerebral haemorrhage or ischaemia, and may explain TIA or stroke in patients without other vascular risk factors.

Bi-allelic JAM2 Variants Lead to Early-Onset Recessive Primary Familial Brain Calcification.

Primary familial brain calcification (PFBC) is a rare neurodegenerative disorder characterized by a combination of neurological, psychiatric, and cognitive decline associated with calcium deposition on brain imaging. To date, mutations in five genes have been linked to PFBC. However, more than 50% of individuals affected by PFBC have no molecular diagnosis. We report four unrelated families presenting with initial learning difficulties and seizures and later psychiatric symptoms, cerebellar ataxia, extrapyramidal signs, and extensive calcifications on brain imaging. Through a combination of homozygosity mapping and exome sequencing, we mapped this phenotype to chromosome 21q21.3 and identified bi-allelic variants in JAM2. JAM2 encodes for the junctional-adhesion-molecule-2, a key tight-junction protein in blood-brain-barrier permeability. We show that JAM2 variants lead to reduction of JAM2 mRNA expression and absence of JAM2 protein in patient's fibroblasts, consistent with a loss-of-function mechanism. We show that the human phenotype is replicated in the jam2 complete knockout mouse (jam2 KO). Furthermore, neuropathology of jam2 KO mouse showed prominent vacuolation in the cerebral cortex, thalamus, and cerebellum and particularly widespread vacuolation in the midbrain with reactive astrogliosis and neuronal density reduction. The regions of the human brain affected on neuroimaging are similar to the affected brain areas in the myorg PFBC null mouse. Along with JAM3 and OCLN, JAM2 is the third tight-junction gene in which bi-allelic variants are associated with brain calcification, suggesting that defective cell-to-cell adhesion and dysfunction of the movement of solutes through the paracellular spaces in the neurovascular unit is a key mechanism in CNS calcification.

The Genetics of Primary Familial Brain Calcification: A Literature Review.

Primary familial brain calcification (PFBC), also known as Fahr's disease, is a rare inherited disorder characterized by bilateral calcification in the basal ganglia according to neuroimaging. Other brain regions, such as the thalamus, cerebellum, and subcortical white matter, can also be affected. Among the diverse clinical phenotypes, the most common manifestations are movement disorders, cognitive deficits, and psychiatric disturbances. Although patients with PFBC always exhibit brain calcification, nearly one-third of cases remain clinically asymptomatic. Due to advances in the genetics of PFBC, the diagnostic criteria of PFBC may need to be modified. Hitherto, seven genes have been associated with PFBC, including four dominant inherited genes (SLC20A2, PDGFRB, PDGFB, and XPR1) and three recessive inherited genes (MYORG, JAM2, and CMPK2). Nevertheless, around 50% of patients with PFBC do not have pathogenic variants in these genes, and further PFBC-associated genes are waiting to be identified. The function of currently known genes suggests that PFBC could be caused by the dysfunction of the neurovascular unit, the dysregulation of phosphate homeostasis, or mitochondrial dysfunction. An improved understanding of the underlying pathogenic mechanisms for PFBC may facilitate the development of novel therapies.

SLC20A2-Associated Idiopathic basal ganglia calcification (Fahr disease): a case family report.

BACKGROUND: Idiopathic basal ganglia calcification (IBGC) is a genetic disorder of the nervous system commonly known as Fahr disease. IBGC patients with a genetic background are considered to have primary familial brain calcification (PFBC), also known as familial basal ganglia calcification (FBGC), or familial Fahr disease. It is a rare degenerative neurological disorder characterized by extensive bilateral basal ganglia calcification that can lead to a range of extrapyramidal symptoms and neuropsychiatric manifestations. Studies have suggested that more than 50 variants of SLC20A2 gene mutations account for approximately 50% of IBGC cases. There is a wide spectrum of mutation types, including frameshift, nonsense, and splice site mutations in addition to deletion and missense mutations. Here we report a case of familial basal ganglia calcification caused by a frameshift mutation in the SLC20A2 gene. We identified a heterozygous mutation in the SLC20A2 gene, c.1097delG (p.G366fs*89). To our knowledge, this mutation site has not been reported before. CASE PRESENTATION: A 57-year-old male patient was admitted to the hospital with "unstable walking and involuntary movements between the eyes and eyebrows for 6 months". Based on the patient's family history, symmetrical calcification foci in the bilateral caudate nucleus head, thalamus, cerebellum and parietal lobe indicated by head CT, and gene test results, the diagnosis of familial Fahr disease caused by mutations in the SLC20A2 gene, c.1097delG p.G366fs*89) was confirmed. CONCLUSION: For the first time, we identified c.1097delG (p.G366fs*89) as a frameshift mutation in the IBGC family. This frameshift mutation caused the condition in this family of patients. This mutation not only broadens the range of known SLC20A2 mutations but also aids in the genetic diagnosis of IBGC.

Characteristics and therapeutic potential of sodium-dependent phosphate cotransporters in relation to idiopathic basal ganglia calcification.

Type-III sodium-dependent phosphate transporters 1 and 2 (PiT 1 and PiT 2, respectively) are proteins encoded by SLC20A1 and SLC20A2, respectively. The ubiquitous distribution of SLC20A1 and SLC20A2 mRNAs in mammalian tissues supports the housekeeping maintenance and homeostasis of intracellular inorganic phosphate (Pi), which is absorbed from interstitial fluid for normal cellular functions. SLC20A2 variants have been found in patients with idiopathic basal ganglia calcification (IBGC), also known as Fahr's disease or primary familial brain calcification (PFBC). Thus, disrupted Pi homeostasis is considered one of the major factors in the pathogenic mechanism of IBGC. In this paper, among the causative genes of IBGC, we focused specifically on PiT2, and its potential for a therapeutic target of IBGC.

Familial idiopathic basal ganglia calcification with a heterozygous missense variant (c.902C>T/p.P307L) in SLC20A2 showing widespread cerebrovascular lesions.

We describe a postmortem case of familial idiopathic basal ganglia calcification (FIBGC) in a 72-year-old Japanese man. The patient showed progressive cognitive impairment with a seven-year clinical course and calcification of the basal ganglia, thalami, and cerebellar dentate nuclei. A novel heterozygous missense variant in SLC20A2 (c.920C>T/p.P307L), a type III sodium-dependent phosphate transporter (PiT-2), was subsequently identified, in addition to typical neuropathological findings of FIBGC, such as capillary calcification of the occipital gray matter, confluent calcification of the basal ganglia and cerebellar white matter, widespread occurrence of vasculopathic changes, cerebrovascular lesions, and vascular smooth muscle cell depletion. Immunohistochemistry for PiT-2 protein revealed no apparent staining in endothelial cells in the basal ganglia and insular cortex; however, the immunoreactivity in endothelial cells of the cerebellum was preserved. Moreover, Western blot analysis identified preserved PiT-2 immunoreactivity signals in the frontal cortex and cerebellum. The variant identified in the present patient could be associated with development of FIBGC and is known to be located at the large intracytoplasmic part of the PiT-2 protein, which has potential phosphorylation sites with importance in the regulation of inorganic phosphate transport activity. The present case is an important example to prove that FIGBC could stem from a missense variant in the large intracytoplasmic loop of the PiT-2 protein. Abnormal clearance of inorganic phosphate in the brain could be related to the development of vascular smooth muscle damage, the formation of cerebrovascular lesions, and subsequent brain calcification in patients with FIBGC with SLC20A2 variants.

Hereditary and non-hereditary etiologies associated with extensive brain calcification: case series.

Cerebral calcification may be caused by several potentially treatable conditions, however, in most cases it does not receive special attention in clinical practice. From the point of view of etiology, the diseases associated with cerebral calcification can be divided into two main groups: idiopathic (mostly incurable) and secondary (potentially treatable). The first group includes mainly the hereditary diseases identified before 2021 (primary familial brain calcification subtypes, previously known as Fahr's disease or Fahr's syndrome). In contrast, the second group includes diseases with cerebral calcification that develop generally as a consequence of metabolic/endocrine/autoimmune abnormalities. The aim of our research was to present hereditary and non-hereditary etiologies associated with extensive brain calcification. We compare the detailed clinical, radiological and laboratory results of 6 patients with prominent cerebral calcification identified in our clinic in the last 3 years (idiopathic and secondary etiologies as well). Our research draws attention to the complexity of the etiologies in the context of cerebral calcification. We recommend, beside NGS-based sequence analyses, the application of array comparative genomic hybridization as well, to identify potential genetic etiologies associated with brain calcification.

SLC20A2 variants cause dysfunctional phosphate transport activity in endothelial cells induced from Idiopathic Basal Ganglia Calcification patients-derived iPSCs.

Idiopathic Basal Ganglia Calcification (IBGC) is a rare neuropsychiatric illness also known as Fahr's disease or Primary Familial Brain Calcification (PFBC). IBGC is caused by SLC20A2 variants, which encodes the inorganic phosphate (Pi) transporter PiT-2, a transmembrane protein associated with Pi homeostasis. We have reported novel SLC20A2 variants in the Japanese population and established an induced pluripotent stem cells (iPSCs) from an IBGC patient carrying a SLC20A2 variant. To investigate the effect of these SLC20A2 variants identified in our previous study, we used Chinese hamster ovary (CHO) cells expressing these variant proteins using the Flp-In system (Flp-In CHO cells), and showed that variant SLC20A2 proteins significantly disrupted the Pi transport activity in Flp-In CHO cells. Endothelial cells (ECs) represent important target cells for elucidating the pathology of IBGC. Using patient-derived iPSCs in this study, we differentiated these cells into ECs and found no significant difference in their differentiation capacity into ECs compared with control iPSCs. However, the Pi transport activity of IBGC patient-derived iPS-ECs was significantly decreased compared with that of control iPS-ECs without changing the gene expression of the other SLC 20 family members. We confirmed that SLC20A2 variants caused the loss of function of the Pi transport activity in both Flp-In CHO cells and disease-specific iPSCs. This is the first report to show an in vitro model of iPSCs in IBGC with patient-identified SLC20A2 variants. These useful tools will help in elucidating IBGC pathogenesis and can be used for screening drug candidates.

A novel de novo PDGFRB variant in a child with severe cerebral malformations, intracerebral calcifications, and infantile myofibromatosis.

The spectrum of clinical consequences of variants in the Platelet derived growth factor receptor beta (PDGFRB) gene is wide. Missense variants leading to variable loss of signal transduction in vitro have been reported in the idiopathic basal ganglia calcification (IBGC) syndrome Type 4. In contrast, gain-of-function variants have been reported in infantile myofibromatosis, Penttinen syndrome, and Kosaki overgrowth syndrome. Here, we report a patient harboring a novel postzygotic variant in PDGFRB (c.1682_1684del, p.[Arg561_Tyr562delinsHis]) and presenting severe cerebral malformations, intracerebral calcifications, and infantile myofibromatosis. This observation expands the phenotype associated with PDGFRB variants and illustrates the wide clinical spectrum linked to dysregulation of PDGFRB.

Clinical features of bipolar disorder with idiopathic basal ganglia calcification: a review of case reports in the literature.

Although idiopathic basal ganglia calcification (IBGC) is associated with various neuropsychiatric disturbances including several cases of bipolar disorder (BD), there has been no systematic review of clinical features of patients with BD and comorbid IBGC. We undertook a literature search to identify case reports of these patients. Most cases showed complex syndromes comprising not only mood disturbance but also cognitive disability and motor symptoms limited to depressive state and had favorable treatment response. These patients should have a careful and repeated psychiatric, neurological, and cognitive assessment to determine an optimal diagnostic and treatment approaches at each clinical stage.

Mineralizing angiopathy presenting with recurrence of basal ganglia stroke following minor head trauma.

Basal ganglia stroke secondary to mineralizing angiopathy of lenticulostriate arteries is a well-recognized clinical entity following minor head trauma in children. Recurrences are uncommon, and the majority of these recurrences occur within a few months of initial insult. We report a 2-year-old boy who developed recurrence of basal ganglia stroke after a latency of 18 months from the time of first unrecognized insult at 6 months of age. The case brings forth the need to recognize the condition of basal ganglia stroke secondary to mineralizing angiopathy considering the risk of recurrence to occur as far as 18 months after the first stroke.

Idiopathic basal ganglia calcification associated with cerebral micro-infarcts: a case report.

BACKGROUND: Idiopathic basal ganglia calcification (IBGC) is a rare neurodegenerative disorder characterized by symmetric intracranial calcium deposition. We report a patient with IBGC associated with cerebral infarction due to impairment of cerebrovascular reactivity based on single-photon emission computed tomography (SPECT) with acetazolamide challenge. CASE PRESENTATION: A 66-year-old male presented with right conjugate deviation, right hemiparesis and total aphasia due to a convulsive seizure. Brain computed tomography showed symmetric calcifications in the bilateral basal ganglia, thalamus, cerebellar dentate nuclei, which were consistent with IBGC. Diffusion-weighted brain magnetic resonance imaging showed multiple small infarctions in the bilateral cerebral subcortical area. In the search for the cause of cerebral infarction, SPECT with acetazolamide challenge revealed heterogeneous impairment of cerebrovascular reactivity in the whole brain, despite the absence of evidence for steno-occlusive changes in proximal arteries. CONCLUSION: Cerebrovascular insufficiency due to the lack of elasticity caused by microvascular calcification might have been one of the pathophysiological features of IBGC in this case. Thus, vascular calcification may cause cerebrovascular disturbance and could lead to ischemic stroke in patients with IBGC.

Anticipation in a family with primary familial brain calcification caused by an SLC20A2 variant.

AIM OF THE STUDY: To describe a family with primary familial brain calcification (PFBC) due to SLC20A2 variant showing possible genetic anticipation. MATERIALS AND METHODS: We conducted historical, genealogical, clinical, and radiologic studies of a family with PFBC. Clinical evaluations including neurological examination and head computed tomography (CT) scans of a proband and her father were performed. They provided additional information regarding other family members. To identify a causative gene variant, we performed whole-exome sequencing for the proband followed by segregation analysis in other affected members using direct sequencing. RESULTS: In this family, nine affected members were identified over four generations. The proband suffered from chronic daily headache including thunderclap headache. We identified an SLC20A2 (c.509delT, p.(Leu170*)) variant in three affected members over three generations. Interestingly, the age of onset became younger as the disease passed through successive generations, suggestive of genetic anticipation. CONCLUSIONS AND CLINICAL IMPLICATIONS: For clinical purpose, it is important to consider thunderclap headache and genetic anticipation in PFBC caused by SLC20A2 variants. Further investigation is required to validate our observation.

Familial idiopathic basal ganglia calcification: Histopathologic features of an autopsied patient with an SLC20A2 mutation.

Idiopathic basal ganglia calcification (IBGC), or Fahr's disease, is a neurological disorder characterized by widespread calcification in the brain. Recently, several causative genes have been identified, but the histopathologic features of the brain lesions and expression of the gene products remain unclear. Here, we report the clinical and autopsy features of a 62-year-old Japanese man with familial IBGC, in whom an SLC20A2 mutation was identified. The patient developed mild cognitive impairment and parkinsonism. A brain CT scan demonstrated abnormal calcification in the bilateral basal ganglia, thalami and cerebellum. An MRI study at this point revealed glioblastoma, and the patient died 6 months later. At autopsy, symmetric calcification in the basal ganglia, thalami, cerebellar white matter and deeper layers of the cerebral cortex was evident. The calcification was observed in the tunica media of small arteries, arterioles and capillaries, but not in veins. Immunohistochemistry using an antibody against type III sodium-dependent phosphate transporter 2 (PiT-2), the SLC20A2 product, demonstrated that astrocytic processes were labeled in several regions in control brains, whereas in the patient, reactivity in astrocytes was apparently weak. Immunoblotting demonstrated a marked decrease of PiT-2 in the patient. There are few autopsy reports of IBGC patients with confirmation of the genetic background. The autopsy features seem informative for better understanding the histogenesis of IBGC lesions.

Brain calcification process and phenotypes according to age and sex: Lessons from SLC20A2, PDGFB, and PDGFRB mutation carriers.

Primary Familial Brain Calcification (PFBC) is a dominantly inherited cerebral microvascular calcifying disorder with diverse neuropsychiatric expression. Three causative genes have been identified: SLC20A2, PDGFRB and, recently, PDGFB, whose associated phenotype has not yet been extensively studied. We included in the largest published case series of genetically confirmed PFBC, 19 PDGFB (including three new mutations), 24 SLC20A2 (including 4 new mutations), and 14 PDGFRB mutation carriers, from two countries (France and Brazil). We studied clinical features and applied our visual rating scale on all 49 available CT scans. Among the symptomatic mutation carriers (33/57, 58%), the three most frequently observed categories of clinical features were psychiatric signs (72.7%, 76.5%, and 80% for PDGFB, SLC20A2, and PDGFRB, respectively), movement disorders (45.5%, 76.5%, and 40%), and cognitive impairment (54.6%, 64.7%, and 40%). The median age of clinical onset was 31 years, 25% had an early onset (before 18) and 25% a later onset (after 53). Patients with an early clinical onset exhibited mostly isolated psychiatric or cognitive signs, while patients with a later onset exhibited mostly movement disorders, especially in association with other clinical features. CT scans rating allowed identifying four patterns of calcification. The total calcification score was best predicted by the combined effects of gene (SLC20A2 > PDGFB > PDGFRB mutations), sex (male), and (increasing) age, defining three risk classes, which correlated with the four patterns of calcification. These calcification patterns could reflect the natural history of the calcifying process, with distinct risk classes characterized by different age at onset or rate of progression.

Idiopathic basal ganglia calcification presenting with obsessive-compulsive symptoms: A case report.

Background: Idiopathic basal ganglia calcification (IBGC), also known as Farh's disease, is a rare neurodegenerative disorder characterized by calcification of the basal ganglia and other brain regions. This disease usually occurs in middle-aged patients and presents with various neurological and psychiatric symptoms. The exact prevalence is unknown; however, population genomic data analysis suggests a prevalence of at least 4.5/10,000 to 3.3/1000, indicating that the disease is more common than previously thought and remains underdiagnosed. Case Presentation: We report the case of a middle-aged Japanese man who attempted suicide twice because of obsessive-compulsive ideation caused by trivial triggers. The patient's psychiatric symptoms resolved relatively quickly after hospitalization, and imaging and genetic testing led to a diagnosis of IBGC. Conclusion: This case report illustrates the importance of including IBGC in the differential diagnosis of psychiatric symptoms that initially develop in middle-aged patients.

Genetic and pathophysiological insights from autopsied patient with primary familial brain calcification: novel MYORG variants and astrocytic implications.

Primary familial brain calcification (PFBC) is a genetic neurological disorder characterized by symmetric brain calcifications that manifest with variable neurological symptoms. This study aimed to explore the genetic basis of PFBC and elucidate the underlying pathophysiological mechanisms. Six patients from four pedigrees with brain calcification were enrolled. Whole-exome sequencing identified two novel homozygous variants, c.488G > T (p.W163L) and c.2135G > A (p.W712*), within the myogenesis regulating glycosidase (MYORG) gene. Cerebellar ataxia (n = 5) and pyramidal signs (n = 4) were predominant symptoms, with significant clinical heterogeneity noted even within the same family. An autopsy of one patient revealed extensive brainstem calcifications, sparing the cerebral cortex, and marked by calcifications predominantly in capillaries and arterioles. The pathological study suggested morphological alterations characterized by shortened foot processes within astrocytes in regions with pronounced calcification and decreased immunoreactivity of AQP4. The morphology of astrocytes in regions without calcification remains preserved. Neuronal loss and gliosis were observed in the basal ganglia, thalamus, brainstem, cerebellum, and dentate nucleus. Notably, olivary hypertrophy, a previously undescribed feature in MYORG-PFBC, was discovered. Neuroimaging showed reduced blood flow in the cerebellum, highlighting the extent of cerebellar involvement. Among perivascular cells constituting the blood-brain barrier (BBB) and neurovascular unit, MYORG is most highly expressed in astrocytes. Astrocytes are integral components of the BBB, and their dysfunction can precipitate BBB disruption, potentially leading to brain calcification and subsequent neuronal loss. This study presents two novel homozygous variants in the MYORG gene and highlights the pivotal role of astrocytes in the development of brain calcifications, providing insights into the pathophysiological mechanisms underlying PFBC associated with MYORG variants.

Homozygous SLC20A2 mutations cause congenital CMV infection-like phenotype.

BACKGROUND: Idiopathic basal ganglia calcification, also known as Fahr's disease, it is a neurological disease characterized by intracranial calcification caused by heterozygous SLC20A2 mutations. Patients with calcifications can either be asymptomatic or show a wide spectrum of neuropsychiatric symptoms, including parkinsonism, tremor, dystonia, ataxia, and seizures. OBJECTIVES: The aim of this study was to investigating the clinical implications of the SLCA20A2 gene and identifying a new phenotype through a family. METHODS: Two siblings with growth retardation, bilateral cataracts, microcephaly, and convulsion were included in the study. The MRI showed cerebral atrophy, corpus callosum hypoplasia, microcalcifications. Chromosomal microarray analysis was performed to identify the existence of copy number variation. The whole exome sequencing analysis of the individual IV-I was performed, and Sanger sequencing was performed for segregation. RESULTS: Whole exome sequencing revealed a homozygous NM_006749.5:c.1794 + 1G > A of the SLC20A2 gene. The Sanger sequencing confirmed the affected siblings were homozygous and the parents were heterozygous. CONCLUSIONS: SLC20A2 gene heterozygous mutations were associated with the adult-onset phenotype, while homozygous SLC20A2 mutations in the two affected siblings we reported in our study resulted in a severe clinic including growth retardation, bilateral cataracts, microcephaly, and convulsion. We showed that biallelic mutations in the SLC20A2 gene that cause the Fahr's disease lead to more severe phenotypes contrary to what is known. The two siblings, showing similar phonotypic and genotypic characteristics, would be the youngest cases in the pediatric age group published in the literature.

Fahr Syndrome: When Dysarthria Doesn't Mean a Stroke.

Fahr syndrome is a rare neurodegenerative disorder, characterized by calcium deposition in the brain. It is usually associated with phosphocalcium metabolism disorders, like hypoparathyroidism, or with genetical predisposition, as seen in Fahr disease. Given the wide array of differential diagnoses medical awareness should be emphasized to prompt diagnosis and management. In this case, we depict a classical presentation of Fahr syndrome, highlighting the differential diagnosis with stroke given the similar clinical signs and symptoms, although pointing out the distinct radiological presentation that raises clinical suspicion for this entity.