Neurodegeneration with Brain Iron Accumulation: Two Additional Cases with Dystonic Opisthotonus

Genetic Landscape of Dystonia in Asian Indians

BACKGROUND

Genomic variations associated with dystonia in Asian Indians remain largely unknown.

OBJECTIVES

To identify genomic alterations associated with dystonia in the Asian Indian population using next generation sequencing approaches.

METHODS

From September 2018 to December 2023, we enrolled 745 individuals including probands with dystonia and family members, in the Indian Movement Disorder Registry and Biobank. Clinical and demographic data were captured on a REDCap platform. We performed whole exome sequencing (WES) on DNA specimens obtained from 267 individuals with isolated, combined or complex dystonia. Variants were classified according to joint guidelines of American College of Medical Genetics and Genomics (ACMG) and Association of Molecular Pathology (AMP).

RESULTS

The mean age of the WES cohort was 33.8 ± 16.2 years, and mean age at onset (AAO) of dystonia was 25.6 ± 17.7 years. 62.2% had isolated dystonia, 7.9% combined and 29.2% had complex phenotypes. WES identified pathogenic/ likely pathogenic variants in 54 patients (20.2%) including 14 novel variants in known dystonia genes. Variants in THAP1 were most common followed by PANK2, GLB1, PLA2G6, TOR1A, ANO3, VPS16, SGCE, SPG7, FTL and other genes. Multifocal/generalized distribution of dystonia [OR: 4.1; 95% CI 1.4-12.2, P = 0.011] and family history [OR: 4.3; 95% CI 2.1-8.9, P < 0.001] were associated with positive yield on WES.

CONCLUSION

THAP1 was the most frequent dystonia associated gene in this cohort. Singleton WES identifiedpotentially pathogenic variants in approximately one out of five patients tested, and contributed to management decisions in 4%.

Spectrum of Truncal Dystonia and Response to Treatment: A Retrospective Analysis

Background:

Presence of truncal dystonia usually points to a secondary cause of dystonia like exposure to dopamine receptor blockers or neurodegenerative illness. Rarely, it can occur as an idiopathic focal or segmental dystonia.

Methods:

Retrospective review of medical records and videos of patients of truncal dystonia presenting in the Botulinum Toxin Clinic of Department of Neurology at Post Graduate Institute of Medical Education and Research, Chandigarh between May 2016 and February 2019.

Results:

A total of 16 patients with predominant truncal dystonia were recruited. There were ten males and six females with mean age of 49.1 ± 15.1 years (range 22–70). Extensor truncal dystonia was the most common (12/16) followed by camptocormia (4/16). Various etiologies included Idiopathic Parkinson’s disease (4/16), Tardive dystonia (5/16), Neurodegeneration with brain iron accumulation (genetically confirmed) (2/16) and idiopathic (5/16). All patients were refractory to a combination of oral medications tried over a period of 1.82 ± 1.93 years. All patients received electromyographic-guided botulinum toxin in paraspinals or rectus abdominis muscles depending upon the type of dystonia. The mean dose of abobotulinum toxin used was 286.7 ± 108.6 units (range 200–500 units) for paraspinals and 297.5 ± 68.5 (range 200–350) for rectus abdominis muscles per session. Average subjective response after botulinum toxin injection session was 31.2 ± 21.5% (range 0–70). No adverse effects were reported.

Conclusion:

Botulinum toxin is an acceptable alternative to patients presenting with medically refractory truncal dystonia and may offer modest benefit.