Careful Phenotypic Characterization of Tremor Phenomenology in a Patient with Spinocerebellar Ataxia Type 12-Tremor Features Do Not Match Those of Essential Tremor.

Background: The tremor characteristics of patients with spinocerebellar ataxia 12 (SCA12) are often likened to those in patients with essential tremor (ET); however, data are sparse, and videotaped tremor examinations are rare. Case Report: A 37-year-old woman with progressive hand and head tremors underwent genetic testing after conventional diagnostics failed to explain her symptoms. A PPP2R2B variation confirmed spinocerebellar ataxia type 12 (SCA12), a condition not previously considered because classical cerebellar signs were absent. The tremor characteristics of this patient differed in numerous respects from those seen in patients with ET. Discussion: Although often likened to ET, under careful scrutiny, the tremor characteristics observed in this patient with SCA12 were inconsistent with those typically seen in ET. Such discrepancies highlight the necessity of careful phenotyping for tremor disorders, particularly in familial cases. Recognizing the specific tremor phenomenology of SCA12 and distinguishing it from ET is crucial to avoid misdiagnosis and to guide appropriate management and familial counseling. Highlights: This report characterizes in detail an early-stage SCA12 patient initially misdiagnosed as essential tremor, underscoring the importance of nuanced clinical assessment and genetic testing in atypical tremor cases. Similar patients should be meticulously phenotyped to prevent misclassification and enhance our understanding of tremor pathophysiology.

MYORG Mutation Heterozygosity Is Associated With Brain Calcification.

BACKGROUND: Biallelic mutations in the MYORG gene were first identified as the cause of recessively inherited primary familial brain calcification. Interestingly, some heterozygous carriers also exhibited brain calcifications. OBJECTIVES: To further investigate the role of single heterozygous MYORG mutations in the development of brain calcifications. METHODS: A nation-wide cohort of Chinese primary familial brain calcification probands was enrolled from March 2016 through September 2019. Mutational analysis of MYORG was performed in 435 primary familial brain calcification probands who were negative for mutations in the other four known primary familial brain calcification-causative genes (SLC20A2, PDGFRB, PDGFB, and XPR1). RESULTS: Biallelic MYORG mutations were identified in 14 primary familial brain calcification patients from 10 unrelated families. Interestingly, 12 heterozygous carriers from seven of these families also exhibited mild-to-moderate brain calcifications. Moreover, single heterozygous mutations were detected in an additional 9 probands and in 7 of their family members affected with brain calcifications. In our cohort, clinical and imaging penetrance of individuals with biallelic mutations were 100%, whereas among individuals with heterozygous mutations, penetrance of imaging phenotype was reduced to 73.7% (28 of 38) and clinical penetrance was much lower. Most (34 of 38) remained asymptomatic whereas 4 carriers had symptoms of uncertain clinical significance (nonspecific depression, epilepsy and late-onset parkinsonism). Compared with individuals with biallelic MYORG mutations, individuals with heterozygous mutations had brain calcifications with much lower calcification scores (P < 2e-16). CONCLUSIONS: Presence of brain calcifications in individuals with heterozygous MYORG mutations suggested a semidominant inheritance pattern with incomplete penetrance. This finding further expanded the genotype-phenotype correlations of MYORG-related primary familial brain calcification. © 2020 International Parkinson and Movement Disorder Society.

[Genetic analysis of a pedigree affected with X-linked adrenoleukodystrophy].

OBJECTIVE: To explore the genetic basis for a pedigree affected with X-linked adrenoleukodystrophy presenting as spastic paraplegia of the lower limbs. METHODS: Genomic DNA was extracted from peripheral blood samples of the patient and his mother. Potential variant was detected with a panel for genes associated with spastic paraplegia. Candidate variant was verified by PCR and Sanger sequencing. RESULTS: Both the proband and his mother presented with walking difficulty. A previously known variant, c.623T to A (p.V208E), was identified in the ABCD1 gene mapped on chromosome X in both. CONCLUSION: X-link adrenoleukodystrophy should be taken into account as a possible diagnosis for this pedigree.

[Analysis of a patient with early-onset Parkinson's disease and PARK7 gene variation].

OBJECTIVE: To explore the genetic basis of a patient with early-onset Parkinson disease from a consanguineous family. METHODS: Homozygosity mapping and Sanger sequencing of cDNA were used to identify the causative mutation. RESULTS: A homozygous missense variation (c.56C>G, p.Thr19Arg) in the PARK7 gene was identified in the patient. In silico analysis suggested the c.56C>G variation to be pathogenic. CONCLUSION: Homozygous c.56C>G variation of the PARK7 gene was the disease-causing variation in this family.

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.

LRP10 in autosomal-dominant Parkinson's disease.

BACKGROUND: Recently, the LRP10 gene has been identified as a novel genetic cause in individuals affected by Parkinson's disease (PD), Parkinson's disease dementia, or dementia with Lewy bodies. OBJECTIVE: We investigated the involvement of LRP10 mutations in Chinese patients with familial PD and reviewed previous studies of LRP10 mutations in patients with PD. METHODS: A mutation analysis of the LRP10 gene was performed in a cohort of 205 unrelated Chinese patients with familial PD. Burden analysis was conducted using data from the Genome Aggregation Database and 5 genetic studies of LRP10 in patients with PD (including our cohort). RESULTS: A total of 3 novel potentially pathogenic variants, c.32T>A (p.L11H), c.1184G>A (p.R395H), and c.1333G>A (p.A445T), were detected in 3 probands of our cohort. However, burden analysis argued against an overrepresentation of variant alleles in patients with PD. CONCLUSIONS: Genetic screening of the LRP10 gene in our cohort may provide independent, albeit limited, evidence for the pathogenicity of LRP10 in familial PD. Burden analysis using data from current studies failed to support the association between LRP10 and PD in general. Thus, more robust replication studies are warranted to determine the involvement of LRP10 in the pathogenesis of PD. © 2019 International Parkinson and Movement Disorder Society.

Evaluation of MYORG mutations as a novel cause of primary familial brain calcification.

BACKGROUND: Very recently, the MYORG gene was identified as a novel causative gene for autosomal-recessive primary familial brain calcification. OBJECTIVE: To investigate the clinical, genetic, and neuroradiological characteristics of primary familial brain calcification patients with biallelic MYORG mutations in China. METHODS: We collected clinical and neuroradiological data of 169 Chinese patients with primary familial brain calcification, including 151 sporadic patients and 18 patients from 13 families compatible with an autosomal-recessive mode of inheritance. Mutational analysis of MYORG was performed in the cohort. RESULTS: We identified four, including three novel, MYORG mutations segregating in four families with 5 patients: one nonsense mutation (c.1431C>A, p.Y477*), one missense mutation (c.687G>T, p.W229C), and two nonframeshift indels (c.348_349insCTGGCCTTCCGC, p.116_117insLAFR; c. 428_442delTGCACTTCTTCATCC, p.143_147delLHFFI). The 12-base-pair insertion, c.348_349insCTGGCCTTCCGC, was found in either homozygous or heterozygous state in 2 probands of our cohort and another Chinese primary familial brain calcification patient previously reported on in the literature. Haplotype analysis of our patients harboring the insertion indicated a founder effect in the ethnic Han Chinese population. To date, biallelic MYORG mutations have been reported in 17 patients (including our cohort). Most patients were symptomatic (13 of 17; 76.5%), and the most recurrent symptoms were movement disorders (10 of 17; 58.8%), cognitive decline (7 of 17; 41.2%), and cerebellar symptoms (6 of 17; 35.3%). All patients had calcifications on comprehensive cranial CT, most frequently located in the basal ganglia (17 of 17; 100%), cerebellum (17 of 17; 100%), subcortical white matter (14 of 17; 82.4%), and thalamus (13 of 17; 76.5%). CONCLUSIONS: We confirmed MYORG as a novel causative gene for primary familial brain calcification and further expanded the mutational and phenotypic spectrum of MYORG-related primary familial brain calcification. © 2018 International Parkinson and Movement Disorder Society.

[Genetic study of a Parkinson's disease pedigree caused by compound heterozygous mutations in PARK2 gene].

OBJECTIVE: To explore the genetic basis for a Chinese pedigree where three siblings were affected with Parkinson's disease. METHODS: Multiple ligation-dependent probe amplification (MLPA) and next-generation sequencing (NGS) were employed to detect the causative mutation. Sanger sequencing of cDNA was also used for verify the effect of mutation on the transcription of RNA. RESULTS: Heterozygous deletion of exon 3 of the PARK2 gene was detected by MLPA, while a heterozygous splice site variant c.619-3G>C was detected by NGS. Both mutations were shown to result in aberrant transcripts of the PARK2 gene (loss of exons 3 and 6, respectively) by Sanger sequencing of cDNA. Both mutations have co-segregated with the disease in the pedigree. CONCLUSION: Compound heterozygous mutations of the PARK2 gene probably underlie the disease in this pedigree. Identification of the splice site variant c.619-3G>C has expanded the mutation spectrum of the PARK2 gene.

Intronic pentanucleotide TTTCA repeat insertion in the SAMD12 gene causes familial cortical myoclonic tremor with epilepsy type 1.

Familial cortical myoclonic tremor with epilepsy is an autosomal dominant neurodegenerative disease, characterized by cortical tremor and epileptic seizures. Although four subtypes (types 1-4) mapped on different chromosomes (8q24, 2p11.1-q12.2, 5p15.31-p15.1 and 3q26.32-3q28) have been reported, the causative gene has not yet been identified. Here, we report the genetic study in a cohort of 20 Chinese pedigrees with familial cortical myoclonic tremor with epilepsy. Linkage and haplotype analysis in 11 pedigrees revealed maximum two-point logarithm of the odds (LOD) scores from 1.64 to 3.77 (LOD scores in five pedigrees were >3.0) in chromosomal region 8q24 and narrowed the candidate region to an interval of 4.9 Mb. Using whole-genome sequencing, long-range polymerase chain reaction and repeat-primed polymerase chain reaction, we identified an intronic pentanucleotide (TTTCA)n insertion in the SAMD12 gene as the cause, which co-segregated with the disease among the 11 pedigrees mapped on 8q24 and additional seven unmapped pedigrees. Only two pedigrees did not contain the (TTTCA)n insertion. Repeat-primed polymerase chain reaction revealed that the sizes of (TTTCA)n insertion in all affected members were larger than 105 repeats. The same pentanucleotide insertion (ATTTCATTTC)58 has been reported to form RNA foci resulting in neurotoxicity in spinocerebellar ataxia type 37, which suggests the similar pathogenic process in familial cortical myoclonic tremor with epilepsy type 1.

A clinical study of the coronal plane deformity in Parkinson disease.

BACKGROUND: Postural deformities in the coronal plane were frequent and disabling complications of PD, which reduces the quality of life of patients. This study aimed to garner greater attention to the Parkinson disease (PD)-related postural trunk deviations in the coronal plane by exploring a method for diagnosis because of the lack of any uniform diagnostic criteria and epidemiological studies. It also aimed to provide correlation data in the Chinese PD patients. METHODS: In this cross-sectional study, 503 consecutive outpatients with PD were enrolled who underwent standardized clinical evaluation. The study recruited 83 PD patients diagnosed with Pisa syndrome (PS). Scoliosis and coronal imbalance were diagnosed accurately by radiographic data. The PD patients were compared based on the Cobb angle and coronal balance for several demographic and clinical variables. RESULTS: PD patients with PS had a prevalence of 16.5%. The prevalence of coronal imbalance and scoliosis was 10.34 and 7.75%, respectively. PD patients with PS were older and had a more severe disease, significantly longer disease duration and treatment duration, and reduced quality of life. The most important finding was that the different morphology of the spinal level had an effect on the severity of coronal balance or Cobb angle. CONCLUSIONS: The present study indicated that the postural deformities in the coronal plane were related to the morphology of the spinal level, especially the position of the Cobb angle. To benefit the PD patients with PS, the full-length standing spine radiographs should be performed as early as possible.

Genetic analysis of the CHCHD2 gene in Chinese patients with familial essential tremor.

Recently, Funayama et al. identified CHCHD2 as a novel causative gene of Parkinson disease (PD). However, the relationship between CHCHD2 and essential tremor (ET) patients was still unknown. Genetic analysis of CHCHD2 gene was conducted in 60 probands of ET families with autosomal dominant inheritance and 90 healthy controls in Chinese population. No pathogenic CHCHD2 mutation was found in ET patients. However, we identified one rare variant, c.5C>T, a reported risk variant for sporadic PD in Japanese populations, and examined the frequency of three common variants. Our results suggested that CHCHD2 mutations may be rare in Chinese familial ET patients.

Genetic analysis of the CHCHD2 gene in a cohort of Chinese patients with Parkinson disease.

CHCHD2 has been recently reported as a causative gene for autosomal dominant Parkinson disease (ADPD) in Japanese populations. Further genetic studies of CHCHD2 in other populations are needed. Herein, we sequenced CHCHD2 gene in 162 patients (90 from ADPD pedigrees, 72 with sporadic Parkinson disease) and 90 healthy controls in Chinese population. We observed 5 exonic variants (c.-34C>A, c.-9T>G, c.5C>T, c.*125G>A, c.*154A>G) including 1 novel variant. No pathogenic mutation was found, suggesting that CHCHD2 mutations may be rare in Chinese ADPD patients.