There is strong evidence for blood-brain and blood-spinal cord barrier dysfunction at the early stages of many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Since impairment of the blood-central nervous system barrier (BCNSB) occurs during the pre-symptomatic stages of ALS, the mechanisms underlying this pathology are likely also involved in the ALS disease process. In this review, we explore how drivers of ALS disease, particularly mitochondrial dysfunction, astrocyte pathology and neuroinflammation, may contribute to BCNSB impairment. Mitochondria are highly abundant in BCNSB tissue and mitochondrial dysfunction in ALS contributes to motor neuron death. Likewise, astrocytes adopt key physical, transport and metabolic functions at the barrier, many of which are impaired in ALS. Astrocytes also show raised expression of inflammatory markers in ALS and ablating ALS-causing transgenes in astrocytes slows disease progression. In addition, key drivers of neuroinflammation, including TAR DNA-binding protein 43 (TDP-43) pathology, matrix metalloproteinase activation and systemic inflammation, affect BCNSB integrity in ALS. Finally, we discuss the translational implications of BCNSB dysfunction in ALS, including the development of biomarkers for disease onset and progression, approaches aimed at restoring BCNSB integrity and in vitro modelling of the neurogliovascular system.
Background
We present the clinical, MRI and CT findings in a case of a new mitochondrial genome mutation (tRNA arginine gene), characterized by brain calcifications which are indicative of Kearns–Sayre syndrome (KSS). Some radiological features resembled those of Fahr’s disease (affecting the PDGFRB gene).
Case presentation
A 36-year-old male presented some typical clinical features of KSS, including onset before 20 years of age, pigmentary retinopathy, progressive external ophthalmoplegia and ptosis. However, the hallmark radiological finding of diffuse calcifications in the nuclear ganglia resembles some cases related to the PDGRFB mutation. Genetic investigation revealed a new mutation in the mitochondrial tRNA-arginine gene.
Conclusions
Brain calcifications are a common feature of mitochondrial diseases, but little is known about their pathophysiology. Here, we describe radiological similarities between a new mitochondrial DNA mutation and other genetic conditions, which are related to Fahr’s disease. These similarities could provide new insights into putative genotype–phenotype correlations.
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