PXE: Unlocking the Mystery of This Rare Genetic Disorder
"A breakthrough in understanding pseudoxanthoma elasticum (PXE) reveals new possibilities for treatment."
Since the early 1900s, when the concept of inborn errors of metabolism was first introduced, scientists have identified and characterized countless metabolic diseases. However, some conditions remain stubbornly resistant to understanding. Pseudoxanthoma elasticum (PXE), a relatively frequent genetic disorder characterized by abnormal calcification in the skin, eyes, and blood vessels, was one such enigma until very recently.
In 2013, researchers finally identified the cause of PXE: a malfunction in a specific biochemical mechanism. This discovery not only shed light on the disease's origins but also opened up potential avenues for new treatments. What makes this particularly exciting is that, until now, PXE has remained largely untreatable.
This article explores the complex journey that led to our current understanding of PXE. We'll break down the key biochemical processes involved, discuss some of the controversies surrounding the condition, and highlight promising new treatment strategies.
Prevalence and Health Impact
PXE is an autosomal-recessive multisystem disorder caused by mutations in ABCC6, with mineralization affecting elastic tissues, especially in the skin, eyes, and blood vessels (Reference URL 1; Reference URL 2). Reported clinical prevalence estimates range from 1 per 100,000 to 1 per 25,000 link.springer.com. PXE is associated with severe visual impairment and peripheral arterial disease, and its manifestations can involve considerable morbidity and mortality (Reference URL 2; Reference URL 3).
What is PXE, and What are the Symptoms?
PXE is a genetic disorder that leads to abnormal calcification throughout the body. This calcification most notably affects the skin, blood vessels, and eyes. The root cause is the buildup of amorphous calcium phosphate, which gradually transforms into hydroxyapatite.
- Autosomal Recessive: PXE is an inherited condition, meaning both parents must carry the faulty gene for a child to be affected.
- Frequency: It is estimated to affect 1 in 50,000 people.
- Gene Defect: The primary cause lies in mutations of the ABCC6 gene. This gene is responsible for producing a protein called multidrug resistance protein 6 (MRP6), now known as ABCC6.
- The ABCC6 Paradox: ABCC6 is mainly found in the liver and kidneys, which raises the question: how can a defect in a liver/kidney protein cause calcification in other parts of the body? This question has fueled debate and research in the field.
Current Research and Clinical Questions
A narrative review discusses lipid metabolism alterations in hereditary inorganic pyrophosphate deficiency syndromes, which involve genes including ABCC6, ENPP1, ANK, ALPL, CD73, and CD39 doi.org. The TEMP-PREVENT study protocol describes a randomized, double-blind, placebo-controlled trial testing cyclical etidronate at 20 mg/kg in PXE patients aged 18 to 55, with ectopic calcification as the focus doi.org. Separately, a study reports that higher arterial calcification volumes measured by CT in PXE patients are associated with a higher risk of a first cardiovascular event .
A Multisystem Disorder with Variable Manifestations
PXE is described as a multisystem disease with manifestations in the skin, eyes, and cardiovascular system pmc.ncbi.nlm.nih.gov. A 2024 review identifies it as an autosomal-recessive disorder caused by ABCC6 mutations and reports that the transporter encoded by ABCC6 is mainly expressed in hepatocytes and promotes ATP efflux sciencedirect.com. A 2026 clinical review links ABCC6 mutations to low levels of pyrophosphate, an inhibitor of ectopic calcification, and to elastic-fiber fragmentation and calcification in the skin, eyes, and vascular system .
Classic PXE and PXE-Like Conditions
The classic PXE phenotype is associated with ABCC6 mutations, but PXE-like skin findings have also been reported in people with mutations in GGCX, a gene involved in γ-carboxylation of Gla-proteins sciencedirect.com. The report describes this finding as expanding the clinical spectrum of PXE-like conditions, while noting that such phenotypes can occur without evidence of ABCC6 mutations sciencedirect.com. MedlinePlus describes PXE itself as a progressive disorder marked by deposits of calcium and other minerals in elastic fibers medlineplus.gov.
Hope for the Future
The discovery of the link between ABCC6, ATP, and PP opens exciting possibilities for treating PXE. Supplementing PP directly or finding ways to increase its levels in the body are now active areas of research.
Systemic Effects on Connective Tissue
PXE is an inherited systemic connective-tissue disease that primarily affects the skin, retina, and cardiovascular system ncbi.nlm.nih.gov. Its characteristic tissue changes include mineralization and fragmentation of elastic fibers, a process described as elastorrhexis ncbi.nlm.nih.gov.
Animal studies have shown promising results with PP supplementation, delaying the onset of calcification. Early-generation bisphosphonates, relatively inexpensive drugs originally developed for other conditions, are also being explored as potential treatments.
These new treatment initiatives for PXE could offer insights and approaches that benefit other disorders of calcium phosphate metabolism, offering hope for a wider range of patients.