Keratoglobus and Deep Stromal Corneal Opacification in a Case of Arterial Tortuosity Syndrome

Ophthalmic Manifestations of Arterial Tortuosity Syndrome: Case Series of Patient and Carriers

PURPOSE

The aim of this study was to report the detailed ophthalmic findings in a young patient with genetically confirmed arterial tortuosity syndrome (ATS) and the findings in 8 family members who were carriers.

METHODS

Nine members of the same Saudi family were assessed at King Khaled Eye Specialist Hospital in Riyadh, Saudi Arabia, for ATS-related ocular changes after homozygosity for the pathogenic variant of SLC2A10 gene was confirmed in 1 member. All family members underwent complete ophthalmic examination, genetic testing, and corneal tomography at presentation and at 6-month follow-up.

RESULTS

All ophthalmic features were manifested in our patient with ATS including schisis-like splitting of the stromal layer with greater peripheral thinning, pannus, deep posterior stromal opacities, myopia, high astigmatism, and keratoglobus. The ocular phenotype was also expressed in some carriers ranging from mild myopia to the full spectrum of corneal abnormalities associated with ATS.

CONCLUSIONS

Our study provided further insights into the phenotype in both patients with ATS and carriers. Annual ophthalmic examination is warranted in both types of patients and must undergo from early life onward to detect progressive ectasia which may necessitate corneal crosslinking.

Corneal stromal deposits in connective tissue disease, a case series

Purpose

We report two cases of refractile, peripheral, corneal stromal deposition in two patients with arterial tortuosity syndrome (ATS) and Ehlers-Danlos syndrome (EDS), two closely related connective tissue diseases (CTDs).

Observations

Patient 1: A 21-year-old man with history of ATS and keratoectasia presented with bilateral peripheral corneal neovascularization with numerous whitish brown, refractile, deep stromal opacities that were circumferential along the inferotemporal cornea. After 3 years of follow-up, the corneal deposits did not progress, but the ectasia did, with significant bilateral corneal steepening and thinning for which the patient was recommended to undergo repeat corneal collagen cross linking. Patient 2: A 26-year-old man with presumed diagnosis of EDS presented with numerous whitish brown, refractile, deep stromal opacities that were circumferential along the temporal cornea in the right eye, and superiorly in the left eye. The left eye had a pseudopterygium involving 50% of the cornea. After 2 years of follow-up, the corneal opacities did not progress; however, the patient underwent primary excision of the pseudopterygium and subsequently had conjunctivalization of the entire cornea. The lesions in both cases resembled those seen in Terrien's marginal degeneration.

Conclusions and importance

Peripheral corneal stromal deposits have never been reported before in EDS or ATS or other connective tissue diseases. This case series may prompt further inquiry and characterization of these findings in patients with CTDs.

Slc2a10 knock-out mice deficient in ascorbic acid synthesis recapitulate aspects of arterial tortuosity syndrome and display mitochondrial respiration defects

Arterial tortuosity syndrome (ATS) is a recessively inherited connective tissue disorder, mainly characterized by tortuosity and aneurysm formation of the major arteries. ATS is caused by loss-of-function mutations in SLC2A10, encoding the facilitative glucose transporter GLUT10. Former studies implicated GLUT10 in the transport of dehydroascorbic acid, the oxidized form of ascorbic acid (AA). Mouse models carrying homozygous Slc2a10 missense mutations did not recapitulate the human phenotype. Since mice, in contrast to humans, are able to intracellularly synthesize AA, we generated a novel ATS mouse model, deficient for Slc2a10 as well as Gulo, which encodes for L-gulonolactone oxidase, an enzyme catalyzing the final step in AA biosynthesis in mouse. Gulo;Slc2a10 double knock-out mice showed mild phenotypic anomalies, which were absent in single knock-out controls. While Gulo;Slc2a10 double knock-out mice did not fully phenocopy human ATS, histological and immunocytochemical analysis revealed compromised extracellular matrix formation. Transforming growth factor beta signaling remained unaltered, while mitochondrial function was compromised in smooth muscle cells derived from Gulo;Slc2a10 double knock-out mice. Altogether, our data add evidence that ATS is an ascorbate compartmentalization disorder, but additional factors underlying the observed phenotype in humans remain to be determined.

Arterial Tortuosity Syndrome: An Ascorbate Compartmentalization Disorder?

Significance: Cardiovascular disorders are the most important cause of morbidity and mortality in the Western world. Monogenic developmental disorders of the heart and vessels are highly valuable to study the physiological and pathological processes in cardiovascular system homeostasis. The arterial tortuosity syndrome (ATS) is a rare, autosomal recessive connective tissue disorder showing lengthening, tortuosity, and stenosis of the large arteries, with a propensity for aneurysm formation. In histopathology, it associates with fragmentation and disorganization of elastic fibers in several tissues, including the arterial wall. ATS is caused by pathogenic variants in SLC2A10 encoding the facilitative glucose transporter (GLUT)10. Critical Issues: Although several hypotheses have been forwarded, the molecular mechanisms linking disrupted GLUT10 activity with arterial malformations are largely unknown. Recent Advances: The vascular and systemic manifestations and natural history of ATS patients have been largely delineated. GLUT10 was identified as an intracellular transporter of dehydroascorbic acid, which contributes to collagen and elastin cross-linking in the endoplasmic reticulum, redox homeostasis in the mitochondria, and global and gene-specific methylation/hydroxymethylation affecting epigenetic regulation in the nucleus. We revise here the current knowledge on ATS and the role of GLUT10 within the compartmentalization of ascorbate in physiological and diseased states. Future Directions: Centralization of clinical, treatment, and outcome data will enable better management for ATS patients. Establishment of representative animal disease models could facilitate the study of pathomechanisms underlying ATS. This might be relevant for other forms of vascular dysplasia, such as isolated aneurysm formation, hypertensive vasculopathy, and neovascularization. Antioxid. Redox Signal. 34, 875-889.