Phenotypic Variability in a Mexican Mestizo Family with Retinal Vasculopathy with Cerebral Leukodystrophy and TREX1 Mutation p.V235Gfs*6

Background

Retinal vasculopathy with cerebral leukodystrophy (RVCL) is an adult-onset, autosomal dominant disease involving microvessels of the brain and eye resulting in central nervous system degeneration with visual disturbances, stroke, motor impairment, and cognitive decline. Frameshift mutations at the C-terminus of TREX1 gene are the molecular cause of this disorder.

Objectives

The objective of this study is to present the different clinical manifestations of RVCL in three-related patients and to investigate the presence of TREX1 mutation in the extended genealogy.

Methods

Multidisciplinary testing was performed in three related patients. Based on their family history, the study was extended to 34 relatives from the same small community. Neurological evaluation, sequencing of TREX1, and presymptomatic diagnosis were offered to all participants.

Results

The patients exhibited the heterozygous TREX1 mutation p.V235Gfs*6, but with phenotypic variability. In addition, 15 relatives were identified as pre-manifest mutation carriers. The remaining participants did not carry the mutation.

Conclusions

This is the figrst report of a large Mexican genealogy with RVCL, where the same TREX1 mutation causes a variation in organ involvement and clinical progression. The early identification and follow-up of individuals at risk may help provide insights into the basis for this variability in presentation.

Renal histopathological findings of retinal vasculopathy with cerebral leukodystrophy

Retinal vasculopathy with cerebral leukodystrophy (RVCL) is a rare autosomal dominant systemic microvascular disease. Neurological disorders and visual disturbance are highlighted as manifestations of RVCL; however, there are few reports focused on nephropathy. Herein, we describe detailed renal histopathological findings in a daughter and father with RVCL, proven by TREX1 genetic analysis. A kidney biopsy of the daughter, 35-year-old with asymptomatic proteinuria, revealed unique and various glomerular changes. Atypical double contour (not tram track-like) of the capillary wall was widely found, an apparent characteristic finding. Glomerular findings were varied due to a combination of new and old segmental mesangial proliferative changes, mesangiolysis, and segmental glomerulosclerosis-like lesions; these changes may be related to endothelial cell damage. Collapsed tufts were also found and thought to be the result of ischemia due to arterial changes. Glomerular findings in a kidney biopsy of the father revealed similarity to the daughter's glomerulus at a relatively advanced stage, but the degree of variety in the glomerular findings was much less. Kidney biopsy findings suggesting endothelial cell damage of unknown etiology need to be considered for possible RVCL.

Hereditary cerebral small vessel disease and stroke

Cerebral small vessel disease is considered hereditary in about 5% of patients and is characterized by lacunar infarcts and white matter hyperintensities on MRI. Several monogenic hereditary diseases causing cerebral small vessel disease and stroke have been identified. The purpose of this systematic review is to provide a guide for determining when to consider molecular genetic testing in patients presenting with small vessel disease and stroke. CADASIL, CARASIL, collagen type IV mutations (including PADMAL), retinal vasculopathy with cerebral leukodystrophy, Fabry disease, hereditary cerebral hemorrhage with amyloidosis, and forkhead box C1 mutations are described in terms of genetics, pathology, clinical manifestation, imaging, and diagnosis. These monogenic disorders are often characterized by early-age stroke, but also by migraine, mood disturbances, vascular dementia and often gait disturbances. Some also present with extra-cerebral manifestations such as microangiopathy of the eyes and kidneys. Many present with clinically recognizable syndromes. Investigations include a thorough family medical history, medical history, neurological examination, neuroimaging, often supplemented by specific examinations e.g of the of vision, retinal changes, as well as kidney and heart function. However molecular genetic analysis is the final gold standard of diagnosis. There are increasing numbers of reports on new monogenic syndromes causing cerebral small vessel disease. Genetic counseling is important. Enzyme replacement therapy is possible in Fabry disease, but treatment options remain overall very limited.

Monogenic causes of stroke: now and the future

Most stroke is multifactorial with multiple polygenic risk factors each conferring small increases in risk interacting with environmental risk factors, but it can also arise from mutations in a single gene. This review covers single-gene disorders which lead to stroke as a major phenotype, with a focus on those which cause cerebral small vessel disease (SVD), an area where there has been significant recent progress with findings that may inform us about the pathogenesis of SVD more broadly. We also discuss the impact that next generation sequencing technology (NGST) is likely to have on clinical practice in this area. The most common form of monogenic SVD is cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, due to the mutations in the NOTCH3 gene. Several other inherited forms of SVD include cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy, retinal vasculopathy with cerebral leukodystrophy, collagen type IV α1 and α2 gene-related arteriopathy and FOXC1 deletion related arteriopathy. These monogenic forms of SVD, with overlapping clinical phenotypes, are beginning to provide insights into how the small arteries in the brain can be damaged and some of the mechanisms identified may also be relevant to more common sporadic SVD. Despite the discovery of these disorders, it is often challenging to clinically and radiologically distinguish between syndromes, while screening multiple genes for causative mutations that can be costly and time-consuming. The rapidly falling cost of NGST may allow quicker diagnosis of these rare causes of SVD, and can also identify previously unknown disease-causing variants.