A Japanese family with primary familial brain calcification presenting with paroxysmal kinesigenic dyskinesia - A comprehensive mutational analysis-

A heterozygous deletion of PDGFB gene causes paroxysmal kinesigenic dyskinesia with primary familial brain calcification

BACKGROUND

Primary familial brain calcification (PFBC) is a neurodegenerative disease characterized with calcium deposition in multiple brain regions. Mutations in PDGFB have been discovered in sporadic and familial PFBC cases. While several known variants displayed loss-of function, no complete deletion of platelet-derived growth factor B (PDGFB) has been reported.

METHODS

For the diagnostic purpose, brain computerized tomography or magnetic resonance imaging scanning and whole-genome sequencing were performed on the proband and family members in the pedigree.

RESULTS

We identified a heterozygous PDGFB complete deletion in a Chinese pedigree. The proband presented with paroxysmal kinesigenic dyskinesia (PKD), a rare symptom in PFBC. The proband's mother carrying the same mutation was asymptomatic.

CONCLUSIONS

For the first time, we reported a PFBC with a heterozygous deletion of PDGFB, and provided evidence of haploinsufficiency in the pathogenesis of PFBC.

Genetic updates on paroxysmal dyskinesias

The paroxysmal dyskinesias are a diverse group of genetic disorders that manifest as episodic movements, with specific triggers, attack frequency, and duration. With recent advances in genetic sequencing, the number of genetic variants associated with paroxysmal dyskinesia has dramatically increased, and it is now evident that there is significant genotype-phenotype overlap, reduced (or incomplete) penetrance, and phenotypic variability. In addition, a variety of genetic conditions can present with paroxysmal dyskinesia as the initial symptom. This review will cover the 34 genes implicated to date and propose a diagnostic workflow featuring judicious use of whole-exome or -genome sequencing. The goal of this review is to provide a common understanding of paroxysmal dyskinesias so basic scientists, geneticists, and clinicians can collaborate effectively to provide diagnoses and treatments for patients.