Arterial Calcification as a Pseudoxanthoma Elasticum-like Manifestation in Beta-Thalassemia: Molecular Mechanisms and Significance

Thalassemia, once associated with limited survival, now sees extended life expectancy due to treatment advancements, but new complications such as pseudoxanthoma elasticum (PXE)-like syndrome are emerging. In fact, thalassemia patients develop PXE-like features more frequently than the general population. These features include skin lesions, ocular changes, and vascular issues like arterial calcifications, all linked to oxidative damage from iron overload. PXE-like syndrome in thalassemia mimics inherited PXE but is acquired. The underlying cause is thought to be oxidative stress due to iron overload, which induces free radicals and damages elastic tissues. Unlike inherited PXE, this form does not involve mutations in the ABCC6 gene, suggesting different pathogenic mechanisms, including abnormal fibroblast metabolism and oxidative processes. The vascular calcification seen in this syndrome often follows elastic fiber degeneration, with proteoglycans and glycoproteins acting as nucleation sites for mineralization. The condition can lead to severe cardiovascular and gastrointestinal complications. Studies have shown a significant incidence of PXE-like skin lesions in thalassemia patients, with some dying from cardiovascular complications. Research on ABCC6, a transporter protein involved in ectopic mineralization, has highlighted its role in various conditions, including PXE, beta-thalassemia, and generalized arterial calcification of infancy. ABCC6 mutations or reduced expression led to ectopic mineralization, affecting cardiovascular, ocular, and dermal tissues. The exact molecular mechanisms linking ABCC6 deficiency to ectopic mineralization remain unclear, though it is known to influence calcification-modulating proteins. This review focuses on the role of ABCC6 in the pathogenesis of calcifications, especially intracranial vascular calcifications in PXE and beta-thalassemia.