A Novel SLC20A2 Mutation Associated with Familial Idiopathic Basal Ganglia Calcification and Analysis of the Genotype-Phenotype Association in Chinese Patients

Primary familial brain calcification presenting with parkinsonism and motor complications caused by a novel SLC20A2 variant: a case report

Primary familial brain calcification (PFBC), also known as Fahr's disease, is a central nervous system calcium deposition disorder with symmetrical basal ganglia calcification. Most PFBC cases are caused by SLC20A2 gene variant. We report a Chinese female patient with PFBC and dopamine-responsive parkinsonism who had motor fluctuations and dyskinesia and recovered effectively after symptomatic medication adjustment. A novel heterozygous missense variant was found by whole-exome sequencing and proven harmful by family validation and genetic analysis. This example expands the phenotype of SLC20A2-associated PFBC patients and shows the clinical efficacy of dopaminergic replacement treatment.

Fahr's Disease: Case Presentation With Facial Numbness

Fahr's disease is a rare hereditary neurological disorder characterized by idiopathic basal ganglia and cerebral cortex calcifications. It presents a wide range of neurological manifestations, including motor dysfunction, sensory deficits, seizures, headaches, visual disturbances, and movement disorders. We present a case report of a 42-year-old female who presented to the accident and emergency department with a stroke alert. Her main symptom was left facial numbness. Otherwise, she was fit and well. A CT scan of her head revealed significant bilateral basal ganglia calcifications rather than ischaemic or haemorrhagic changes. Blood tests showed normal serum calcium, normal phosphate, and normal parathyroid hormone levels. Upon further inquiry, she mentioned that her sister had been diagnosed with similar findings on a brain scan. Subsequently, an MRI scan of her brain was performed, which suggested Fahr's disease. Currently, there is no definitive management available, so a conservative management approach is usually employed based on symptomatology. This case is particularly interesting due to its rarity, strong genetic inheritance, and the development of a management plan.

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.

Biallelic XPR1 mutation associated with primary familial brain calcification presenting as paroxysmal kinesigenic dyskinesia with infantile convulsions

BACKGROUND

Mutations in the XPR1 gene are associated with primary familial brain calcifications (PFBC). All reported mutations are missense and inherited as an autosomal dominant trait. PFBC patients exhibited movement disorders, neuropsychiatric symptoms, and other associated symptoms with diverse severity, even within the same family.

MATERIALS AND METHODS

We identified and enrolled a patient with PFBC. Clinical data were comprehensively collected, including the age of onset, seizure types and frequency, trigger factors of paroxysmal dyskinesia, response to drugs, and general and neurological examination results. Whole-exome sequencing (WES) was performed to detect pathogenic variants. We further systematically reviewed the phenotypic and genetic features of patients with XPR1 mutations.

RESULTS

The patient showed bilateral calcification involving basal ganglia and cerebellar dentate. Clinically, he presented as paroxysmal kinesigenic dyskinesia with infantile convulsions (PKD/IC) with favorable outcome. We identified a compound heterozygous XPR1 mutation (c.786_789delTAGA/p.D262Efs*6, c.1342C>T/p.R448W), which were inherited from unaffected parents respectively. Further literature review shows a wide range of clinical manifestations of patients with XPR1 mutations, with movement disorders being the most common.

CONCLUSIONS

This is the first report of biallelic mutations in XPR1. The findings suggest for the first time a possible link between PKD/IC and XPR1 mutations.

Evaluation of Changes in Quality Improvement Knowledge Following a Formal Educational Curriculum Within a Statewide Learning Collaborative

OBJECTIVE

Our objectives were to (1) develop a curriculum based upon participants' needs, (2) evaluate baseline QI knowledge of the Illinois Surgical Quality Improvement Collaborative (ISQIC) members, and (3) evaluate the effectiveness of the educational curriculum.

DESIGN

The Surgeon Champion (SC), Surgical Clinical Reviewer (SCR), and QI Designee at each ISQIC hospital completed a QI curriculum containing online modules and in-person trainings. A surgical adaptation of QI-KAT, a validated QI knowledge assessment with multiple-choice and free-response sections, was administered pre- and postcurriculum. Three blinded educators scored each exam using a rubric-based scoring tool (54 total points).

SETTING

The ISQIC is a 52-hospital learning collaborative. Generally, ISQIC participants had little prior formal training or experience with quality improvement.

RESULTS

Among 52 hospitals, 144 pretests and 112 post-tests were collected. Mean scores increased from 66% (35.6 points) to 77% (41.6 points; p < 0.001). Across all hospitals, all participant groups scored higher on the post-test (SCs 15%, SCRs 21%, QI Designees 17%). There was no significant difference in post-test mean scores among different team members: SCs 44 points, SCRs 42 points, QI Designees 44 points, (p = 0.76). When the post-test scores were aggregated at the hospital level, hospitals with new surgical QI programs improved more than hospitals with established programs (new 18%, established 11%, p < 0.05).

CONCLUSIONS

QI knowledge significantly improved after completion of the ISQIC curriculum. These data support the value of formalized curricula to rapidly advance QI knowledge and application skills as a foundation for implementing QI initiatives.

[Basal ganglia calcification]

Calcifications of the basal ganglia are frequently seen on the cerebral CT scans and particularly in the globus pallidus. Their frequency increases physiologically with age after 50 years old. However, pathological processes can also be associated with calcium deposits in the gray nuclei, posterior fossa or white matter. Unilateral calcification is often related to an acquired origin whereas bilateral ones are mostly linked to an acquired or genetic origin that will be sought after eliminating a perturbation of phosphocalcic metabolism. In pathological contexts, these calcifications may be accompanied by neurological symptoms related to the underlying disease: Parkinson's syndrome, psychiatric and cognitive disorders, epilepsy or headache. The purpose of this article is to provide a diagnostic aid, in addition to clinical and biology, through the analysis of calcification topography and the study of different MRI sequences.

Novel SLC20A2 variant in a Japanese patient with idiopathic basal ganglia calcification-1 (IBGC1) associated with dopa-responsive parkinsonism

Idiopathic basal ganglia calcification-1 (IBGC1) is an autosomal dominant disorder characterized by calcification in the basal ganglia, which can manifest a range of neuropsychiatric symptoms, including parkinsonism. We herein describe a 64-year-old Japanese IBGC1 patient with bilateral basal ganglia calcification carrying a novel SLC20A2 variant (p.Val322Glufs*92). The patient also presented with dopa-responsive parkinsonism with decreased dopamine transporter (DAT) density in the bilateral striatum and decreased cardiac ¹²³I-meta-iodobenzylguanidine uptake.

Underestimated disease prevalence and severe phenotypes in patients with biallelic variants: A cohort study of primary familial brain calcification from China

BACKGROUND

Primary familial brain calcification (PFBC) is a rare calcifying disorder of the brain with extensive clinical and genetic heterogeneity. Its prevalence is underestimated due to clinical selection bias (compared with symptomatic PFBC patients, asymptomatic ones are less likely to undergo genetic testing).

METHODS

A total of 273 PFBC probands were enrolled in a multicenter retrospective cohort study by two different approaches. In Group I (nonsystematic approach), 37 probands diagnosed at our clinic were enrolled. In Group II (systematic approach), 236 probands were enrolled by searching the medical imaging databases of 50 other hospitals using specific keywords. Genetic testing of four genes known to be causative of autosomal dominant PFBC was performed in all probands using cDNA. All identified variants were further confirmed using genomic DNA and classified according to ACMG-AMP recommendations.

RESULTS

Thirty-two variants including 22 novel variants were detected in 37 probands. Among these probands, 83.8% (31/37) were asymptomatic. Two probands with homozygous pathogenic SLC20A2 variants presented more severe brain calcification and symptoms. Based on the variant detection rate of probands in Group II, we extrapolated an overall minimal prevalence of PFBC of 6.6 per 1,000, much higher than previously reported (2.1 per 1000).

CONCLUSIONS

We identified a higher proportion of genetically confirmed PFBC probands who were asymptomatic. These patients would be overlooked due to clinical selection bias, leading to underestimation of the disease prevalence. Considering that PFBC patients with biallelic variants had more severe phenotypes, this specific condition should be focused on in genetic counseling.

Spectrum of SLC20A2, PDGFRB, PDGFB, and XPR1 mutations in a large cohort of patients with primary familial brain calcification

Primary familial brain calcification (PFBC) is a rare neurodegenerative disorder with four causative genes (SLC20A2, PDGFRB, PDGFB, and XPR1) that have been identified. Here, we aim to describe the mutational spectrum of four causative genes in a series of 226 unrelated Chinese PFBC patients. Mutations in four causative genes were detected in 16.8% (38/226) of PFBC patients. SLC20A2 mutations accounted for 14.2% (32/226) of all patients. Mutations in the other three genes were relatively rare, accounting for 0.9% (2/226) of all patients, respectively. Clinically, 44.8% of genetically confirmed patients (probands and relatives) were considered symptomatic. The most frequent symptoms were chronic headache, followed by movement disorders and vertigo. Moreover, the total calcification score was significantly higher in the symptomatic group compared to the asymptomatic group. Functionally, we observed impaired phosphate transport induced by seven novel missense mutations in SLC20A2 and two novel mutations in XPR1. The mutation p.D164Y in XPR1 might result in low protein expression through an enhanced proteasome pathway. In conclusion, our study further confirms that mutations in SLC20A2 are the major cause of PFBC and provides additional evidence for the crucial roles of phosphate transport impairment in the pathogenies of PFBC.