The first Japanese case of primary familial brain calcification caused by an MYORG variant

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.

A novel MYORG mutation causes primary familial brain calcification with migraine: Case report and literature review

Primary familial brain calcification (PFBC) is a disorder in which pathologic calcification of the basal ganglia, cerebellum, or other brain regions with bilateral symmetry occurs. Common clinical symptoms include dysarthria, cerebellar symptoms, motor deficits, and cognitive impairment. Genetic factors are an important cause of the disease; however autosomal recessive (AR) inheritance is rare. In 2018, the myogenesis-regulated glycosidase (MYORG) gene was the first to be associated with AR-PFBC. The present case is a 24-year-old woman with AR-PFBC that presented with migraine at the age of 16 years. Symmetrical patchy calcifications were seen in the bilateral cerebellopontine nuclei, thalamus, basal ganglia, and radiocoronal area on computed tomography and magnetic resonance imaging. AR-PFBC with migraine as the main clinical symptom is rare. Whole-exome sequencing revealed a compound heterozygous mutation in the MYORG gene, one of which has not been previously reported. Our case highlights the pathogenic profile of the MYORG gene, and demonstrates the need for exclusion of calcium deposits in the brain for migraine patients with AR inheritance.

Mutation Analysis of MYORG in a Chinese Cohort With Primary Familial Brain Calcification

Primary familial brain calcification (PFBC) is a progressive neurological disorder manifesting as bilateral brain calcifications in CT scan with symptoms as parkinsonism, dystonia, ataxia, psychiatric symptoms, etc. Recently, pathogenic variants in MYORG have been linked to autosomal recessive PFBC. This study aims to elucidate the mutational and clinical spectrum of MYORG mutations in a large cohort of Chinese PFBC patients with possible autosomal recessive or absent family history. Mutational analyses of MYORG were performed by Sanger sequencing in a cohort of 245 PFBC patients including 21 subjects from 10 families compatible with a possibly autosomal-recessive trait and 224 apparently sporadic cases. In-depth phenotyping and neuroimaging features were investigated in all patients with novel MYORG variants. Two nonsense variants (c.442C > T, p. Q148*; c.972C > A, p. Y324*) and two missense variants (c.1969G>C, p. G657R; c.2033C > G, p. P678R) of MYORG were identified in four sporadic PFBC patients, respectively. These four novel variants were absent in gnomAD, and their amino acid were highly conserved, suggesting these variants have a pathogenic impact. Patients with MYORG variants tend to display a homogeneous clinical spectrum, showing extensive brain calcification and parkinsonism, dysarthria, ataxia, or vertigo. Our findings supported the pathogenic role of MYORG variants in PFBC and identified two pathogenic variants (c.442C > T, c.972C > A), one likely pathogenic variant (c.2033C > G), and one variant of uncertain significance (c.1969G>C), further expanding the genetic and phenotypic spectrum of PFBC-MYORG.

First pediatric case with primary familial brain calcification due to a novel variant on the MYORG gene and review of the literature

Variants in the myogenesis-regulating glycosidase (MYORG) gene which is known as the first autosomal recessive gene that has been associated with primary familial brain calcification (AR-PFBC). Although adult patients have been reported, no pediatric case has been reported until now. Herein, we review the clinical and radiological features of all AR- PFBC patients with biallelic variants in the MYORG gene who were reported until now, and we report the youngest patient who has a novel homozygous variant. Since the first identification of the MYORG gene in 2018, 74cases of MYORG variants related to AR-PFBC were evaluated. The ages of symptom onset of the patients ranged between 7.5 and 87 years. The most frequent clinical courses were speech impairment, movement disorder and cerebellar signs. All patients showed basal ganglia calcification usually bilaterally with different severities. Conclusion; herein, we reported the first pediatric patient in the literature who had a novel homozygous variant in the MYORG gene with mild clinic findings.