Characterization of pseudoxanthoma elasticum-like lesions in the skin of patients with beta-thalassemia

Acquired disorders of elastic tissue: part I. Increased elastic tissue and solar elastotic syndromes

Elastic fibers in the extracellular matrix are an integral component of dermal connective tissue. The resilience and elasticity required for normal structure and function of the skin may be attributed to the network of elastic tissue. Advances in our understanding of elastic tissue physiology provide a foundation for studying the pathogenesis of elastic tissue disorders. Many acquired disorders are nevertheless poorly understood due to the paucity of reported cases. Several acquired disorders in which accumulation or elastotic degeneration of dermal elastic fibers produces prominent clinical and histopathologic features have recently been described. They include elastoderma, linear focal elastosis, and late-onset focal dermal elastosis and must be differentiated from better-known disorders, among them acquired pseudoxanthoma elasticum, elastosis perforans serpiginosa, and Favré-Racouchot syndrome. Learning objective At the conclusion of this learning activity, participants should understand the similarities and differences between acquired disorders of elastic tissue that are characterized by an increase in elastic tissue, as well as the spectrum of solar elastotic dermatoses.

Rupture of chordae tendineae in patients with β-thalassemia

Cardiac disease is the primary cause of mortality in beta-thalassemia patients. Except for ventricular dysfunction and pulmonary hypertension that represent the main forms of heart disease in these patients, valvular abnormalities including valvular regurgitation, endocardial thickening and calcification and mitral valve prolapse have also been described. Here we present two patients with thalassemia major and mitral chordal rupture, a previously undescribed abnormality in this population. Pathogenesis of this finding may involve thalassemia-related pseudoxanthoma elasticum-like syndrome, a diffuse elastic tissue defect, which is observed with a notable frequency in these patients and has been associated with numerous cardiovascular complications, including valvular ones.

Acquired Pseudoxanthoma elasticum-like syndrome in beta-thalassaemia patients

A significant number of patients diagnosed with beta-thalassaemia develop clinical and histopathological manifestations similar to those of an inherited disorder called Pseudoxanthoma elasticum (PXE). The inherited PXE is caused by mutations in the ATP-binding cassette, subfamily C (CFTR/MRP), member 6 (ABCC6) gene and is characterized by mineralized elastic fibres in dermal, vascular and ocular tissues. As no disease-causing variant was found in the ABCC6 gene of 10 beta-thalassaemia patients with a PXE-like phenotype, the present study suggests that the PXE-like symptoms in these beta-thalassaemic patients are not related to ABCC6 mutations.

Pseudoxanthoma elasticum: a clinical, histopathological, and molecular update

Pseudoxanthoma elasticum is an autosomally inherited disorder that is associated with the accumulation of mineralized and fragmented elastic fibers in the skin, Bruch's membrane in the retina, and vessel walls. The ophthalmic and dermatologic expression of pseudoxanthoma elasticum and its vascular complications are heterogeneous, with considerable variation in phenotype, progression, and mode of inheritance. Using linkage analysis and mutation detection techniques, mutations in the ABCC6 gene were recently implicated in the etiology of pseudoxanthoma elasticum. ABCC6 encodes the sixth member of the ATP-binding cassette transporter and multidrug resistance protein family (MRP6). In humans, this transmembrane protein is highly expressed in the liver and kidney. Lower expression was found in tissues affected by pseudoxanthoma elasticum, including skin, retina, and vessel walls. So far, the substrates transported by the ABCC6 protein and its physiological role in the etiology of pseudoxanthoma elasticum are not known. A functional transport study of rat MRP6 suggests that small peptides such as the endothelin receptor antagonist BQ123 are transported by MRP6. Similar molecules transported by ABCC6 in humans may be essential for extracellular matrix deposition or turnover of connective tissue at specific sites in the body. One of these sites is Bruch's membrane. This review is an update on etiology of pseudoxanthoma elasticum, including its clinical and genetic features, pathogenesis, and biomolecular basis.

Pseudoxanthoma elasticum

Pseudoxanthoma elasticum (PXE) is a heritable disease characterized by dermal, ocular, and vascular lesions that result from degeneration of the elastic fibers. Recently, the ATP-binding cassette subfamily C member 6 (ABCC6) gene has been demonstrated to be responsible for PXE, and 43 mutations have been identified to date. However, it is still unknown now mutations in the ABCCC6 gene can lead to manifestations of PXE.

Cardiovascular involvement in thalassaemic patients with pseudoxanthoma elasticum-like skin lesions: a long-term follow-up study

BACKGROUND

Congenital haemolytic anaemia may be associated with pseudoxanthoma elasticum (PXE)-like clinical manifestations.

METHODS

The cardiovascular system of 14 homozygous and double heterozygous beta-thalassaemia patients with skin and retinal vessel alterations similar to those in genetic PXE was analysed over a period of 12 years and compared with that of 13 relatives (five sets of parents, one single parent, two thalassaemic brothers), and that of the control group composed of 16, age- and sex-matched, thalassaemic patients.

RESULTS

All patients with clinical PXE-like skin lesions exhibited, by light and electron microscopy, dermal alterations and mineralization of elastic fibres identical to those typical of inherited PXE. None of the relatives and none of the control group showed clinical or structural findings of PXE. The follow-up started in 1988. After 12 years of clinical observation, six patients showed dramatic progression of skin involvement, angioid streaks had progressed in two subjects. One patient had recurrent gastrointestinal bleeding and underwent partial stomach removal for gastric artery aneurysm, one underwent colon resection for intestinal infarct, one patient had a transitory ischaemic attack, one died after an intracranial haemorrhage, two patients died from cardiovascular disease and one from neoplasia.

CONCLUSIONS

Thalassaemic patients with PXE-like skin lesions also manifest PXE-like vessel alterations that progress with time. Considering the severe outcome of these lesions, accurate monitoring should be routinely performed on the cardiovascular system of thalassaemic patients with PXE-like skin manifestations.

Pseudoxanthoma elasticum: report of a case without any mutations in 5 exons of the MRP6 gene

Pseudoxanthoma elasticum (PXE) is an inherited systemic disorder of connective tissue. We describe a patient with PXE who does not have mutations in exons 16, 24, 27, 28, and 30 of the MRP6 gene.

Elastic tissue abnormalities resembling pseudoxanthoma elasticum in beta thalassemia and the sickling syndromes

The development of clinical and histopathologic manifestations of a diffuse elastic tissue defect, resembling inherited pseudoxanthoma elasticum (PXE), has been encountered with a notable frequency in patients with beta thalassemia, sickle cell disease, and sickle thalassemia. The PXE-like clinical syndrome, consisting of skin, ocular, and vascular manifestations, has a variable severity in these hemoglobinopathies and it is age-dependent, with a generally late onset, after the second decade of life. The defect is believed to be acquired rather than inherited and related to the consequences of the primary disease. The high prevalence of the findings implicates the elastic tissue injury as one of the main comorbid abnormalities encountered in beta thalassemia and the sickling syndromes. In these patients a number of complications, sometimes serious, has been recognized to be related to ocular and vascular elastic tissue defects. Because several organ systems are involved, each medical specialty should be aware of the phenomenon. This coexistence, on the other hand, introduces a novel pathogenetic aspect of PXE and an important research challenge.