Peripheral Interventions in Patients with Pseudoxanthoma Elasticum (PXE)

[Pseudoxanthoma elasticum-Novel therapeutic approaches on the horizon?]

Pseudoxanthoma elasticum (PXE) is an inherited mineralization disorder that leads to calcification of elastic fibers. The ocular characteristics arise due to the calcification of Bruch's membrane, which is located between the retinal pigment epithelium and the choriocapillaris. Despite major scientific progress in understanding the underlying pathological mechanism in recent years, no causal treatment has so far been established. Therefore, the management of patients is currently limited to the treatment of secondary complications, such as intravitreal anti-vascular endothelial growth factor (VEGF) injections in cases of exudative neovascularization. This article discusses upcoming studies that aim to reduce ectopic mineralization. To confirm the diagnosis and possible inclusion in such studies a second assessment should therefore be carried out in a specialized center for PXE.

Successful Pedal Bypass in a Patient With Pseudoxanthoma Elasticum

OBJECTIVES

Pseudoxanthoma elasticum (PXE) is a rare metabolic disease, causing calcification in the arterial media layer and further peripheral artery disease (PAD). A high rate of failure has been reported after endovascular and open surgical management of PAD among patients with PXE. Critical limb ischemia (CLI) rarely develops in PXE, and there are only few reports of its treatment.

METHODS

We present a case report of a 57 year-old female diagnosed with pseudoxanthoma elasticum (PXE). She presented with critical limb ischemia (CLI) and was successfully treated with pedal bypass using the great saphenous vein.

RESULTS

Despite obtaining suboptimal outcomes through the initial approach of percutaneous transluminal angioplasty to treat critical limb ischemia, the subsequent bypass operation proved to be a success. At the first follow-up appointment at 1 month, the patient was asymptomatic and the ulceration had almost healed. The patient underwent an ultrasound examination at 3, 6, 12, and 24 months after discharge, and the surveillance was uncomplicated.

CONCLUSIONS

With a clear indication for surgery, limb-threatening ischemia can be successfully treated with distal bypass, if necessary, in patients with PXE similarly to atherosclerotic PADs. Appropriate diagnostic and surveillance imaging and the utilization of a multidisciplinary team are key components for effective management of PAD in patients with PXE.

Arterial calcification volume is associated with a higher risk of cardiovascular events in pseudoxanthoma elasticum

BACKGROUND AND AIMS

Pseudoxanthoma elasticum (PXE) patients have more arterial calcification due to lower levels of inorganic pyrophosphate, caused by mutations in the ABCC6 gene, but the relation with vascular complications is poorly understood. Because of the slow progressing nature of arterial disease in PXE patients, there is a need for a valid and reliable intermediate endpoint to be used in future clinical trials. Arterial calcification measured on computed tomography (CT) is a promising candidate, if associated with future cardiovascular events. We aimed to establish the relation between arterial calcification measured on CT and future cardiovascular events in patients with PXE.

METHODS

In this prospective cohort study, patients with PXE from the Dutch UMC Utrecht Expertise Center for PXE (UECP) were included. Arterial calcification volume was measured on low dose full body CT scans. Patient were followed for incident cardiovascular events. The relation between arterial calcification and the risk of cardiovascular events was analyzed using Cox proportional hazard models.

RESULTS

In 326 patients (median follow-up 6.0, IQR 3.8-8.2 years) 41 cardiovascular events were observed (21 events per 1000 person years). In patients with no cardiovascular history, there was a significant relation between the log arterial calcification volume at baseline and future cardiovascular events (adjusted HR: 1.87, 95 % CI: 1.14-3.09, per 1 log unit increase in arterial calcification). There was no relation in patients with clinical manifest cardiovascular disease at baseline between arterial calcification volume and future cardiovascular events.

CONCLUSIONS

Higher arterial calcification volumes on CT in PXE patients are associated with a higher risk of a first cardiovascular event. This cohort study suggests that arterial calcification can be used as an intermediate endpoint in studies evaluating interventions to lower the risk of cardiovascular events.

Clinical Approach to Genetic Cerebral Arteriopathy in the Adult Patient With Ischemic Stroke

Genetic arteriopathies leading to stroke in adults constitute a diverse group of cerebrovascular disorders with distinct etiologies, pathophysiologic mechanisms, and clinical presentations. As imaging modalities better delineate subtle changes in cerebral vasculature and access to genetic testing increases, the detection rate for these conditions is expected to rise, particularly among young adults with idiopathic cerebral arteriopathy and stroke. Adults with stroke in the setting of a genetic cerebral arteriopathy often present with few traditional stroke risk factors and, in certain cases, have characteristic clinical features, cerebrovascular imaging findings, and often concurrent systemic vasculopathy, such as aortopathy, which are important to recognize. Given that there are over 50 recognized genetic cerebral arteriopathies that can cause ischemic and hemorrhagic stroke in young adults, it can be a significant diagnostic challenge for the practicing neurologist when faced with a genetic cerebral arteriopathy, because clinical algorithms for a systematic approach to genetic cerebral arteriopathies are lacking. In this review, we present a phenotype-driven, clinically oriented algorithm to guide the diagnostic workup when suspecting a genetic cerebral arteriopathy in an adult patient while highlighting the genetic basis of each disease, molecular mechanisms, clinical manifestations, diagnostic approaches, and emerging therapeutic strategies. Moreover, given the lack of widely available gene panels for diagnostic germline testing for genetic cerebral arteriopathies, we propose key genes to be tested and focused on in each clinical scenario, to better decipher the underlying diagnosis in these rare conditions.

Cardiovascular Manifestations of Pseudoxanthoma Elasticum: Pathophysiology, Management, and Research

Pseudoxanthoma elasticum is a rare genetic disorder characterized by calcification of elastic fibers in the connective tissue. The abundance of elastic tissues at these sites: skin, eyes, and heart make them the most affected systems. It has multifactorial pathogenesis, meaning, it manifests due to both environmental and genetic factors, but ABCC6 gene mutation plays an important role. This gene is responsible for causing defective MRP6 protein which in return is required for cell transport in the connective tissue. The clinical features range from minor skin lesions to fatal cardiovascular complications. Thus, it is important to diagnose it early and give appropriate treatment. This article provides insight into the cardiovascular manifestations of pseudoxanthoma elasticum, its diagnosis and management plans.

Cyclical Etidronate Reduces the Progression of Arterial Calcifications in Patients with Pseudoxanthoma Elasticum: A 6-Year Prospective Observational Study

Background: Pseudoxanthoma elasticum (PXE), a rare genetic disorder presenting with slowly progressing calcification of various tissues, including the arteries, is caused by mutations in the ABCC6 gene that lead to the reduction of pyrophosphate, a natural inhibitor of calcification. We showed that, compared to a placebo, the cyclical administration of etidronate, a stable pyrophosphate analog, significantly reduced arterial calcification assessed by low-dose CT scans after one year. The aim of the present prospective, single center, observational cohort study was the assessment of the efficacy and safety of cyclical etidronate in patients treated for periods longer than one year. Methods: Seventy-three patients were followed for a median of 3.6 years without etidronate and 2.8 years with etidronate, and each patient served as their own control. Results: The median absolute yearly progression of total calcification volume during the period with etidronate (388 [83-838] µL) was significantly lower than that without etidronate (761 [362-1415] µL; p < 0.001). The rates of the relative progression of arterial calcification were 11.7% (95% CI: 9.6-13.9) without etidronate compared to 5.3% (95% CI: 3.7-7.0) with etidronate, after adjustment for confounders. Conclusions: The cyclical administration of etidronate for nearly 3 years significantly reduced the progression rate of arterial calcification in patients with PXE with pre-existing calcifications without any serious adverse effects.

Mitochondrial Dysfunction and Oxidative Stress in Hereditary Ectopic Calcification Diseases

Ectopic calcification (EC) is characterized by an abnormal deposition of calcium phosphate crystals in soft tissues such as blood vessels, skin, and brain parenchyma. EC contributes to significant morbidity and mortality and is considered a major health problem for which no effective treatments currently exist. In recent years, growing emphasis has been placed on the role of mitochondrial dysfunction and oxidative stress in the pathogenesis of EC. Impaired mitochondrial respiration and increased levels of reactive oxygen species can be directly linked to key molecular pathways involved in EC such as adenosine triphosphate homeostasis, DNA damage signaling, and apoptosis. While EC is mainly encountered in common diseases such as diabetes mellitus and chronic kidney disease, studies in rare hereditary EC disorders such as pseudoxanthoma elasticum or Hutchinson-Gilford progeria syndrome have been instrumental in identifying the precise etiopathogenetic mechanisms leading to EC. In this narrative review, we describe the current state of the art regarding the role of mitochondrial dysfunction and oxidative stress in hereditary EC diseases. In-depth knowledge of aberrant mitochondrial metabolism and its local and systemic consequences will benefit the research into novel therapies for both rare and common EC disorders.