Elastic tissue abnormalities in inherited haemolytic syndromes

Retinal abnormalities in β-thalassemia major

Patients with beta (β)-thalassemia (β-TM: β-thalassemia major, β-TI: β-thalassemia intermedia) have a variety of complications that may affect all organs, including the eye. Ocular abnormalities include retinal pigment epithelial degeneration, angioid streaks, venous tortuosity, night blindness, visual field defects, decreased visual acuity, color vision abnormalities, and acute visual loss. Patients with β-thalassemia major are transfusion dependent and require iron chelation therapy to survive. Retinal degeneration may result from either retinal iron accumulation from transfusion-induced iron overload or retinal toxicity induced by iron chelation therapy. Some who were never treated with iron chelation therapy exhibited retinopathy, and others receiving iron chelation therapy had chelator-induced retinopathy. We will focus on retinal abnormalities present in individuals with β-thalassemia major viewed in light of new findings on the mechanisms and manifestations of retinal iron toxicity.

Fibroblast involvement in soft connective tissue calcification

Soft connective tissue calcification is not a passive process, but the consequence of metabolic changes of local mesenchymal cells that, depending on both genetic and environmental factors, alter the balance between pro- and anti-calcifying pathways. While the role of smooth muscle cells and pericytes in ectopic calcifications has been widely investigated, the involvement of fibroblasts is still elusive. Fibroblasts isolated from the dermis of pseudoxanthoma elasticum (PXE) patients and of patients exhibiting PXE-like clinical and histopathological findings offer an attractive model to investigate the mechanisms leading to the precipitation of mineral deposits within elastic fibers and to explore the influence of the genetic background and of the extracellular environment on fibroblast-associated calcifications, thus improving the knowledge on the role of mesenchymal cells on pathologic mineralization.

N-terminal natriuretic peptide and ventilation-perfusion lung scan in sickle cell disease and thalassemia patients with pulmonary hypertension

The aim of this study was to determine the prevalence of pulmonary hypertension (PH) in sickle cell disease and thalassemia patients in relation to clinical and laboratory parameters of hemolysis and hemosidersosis, as well as plasma N-terminal pro-brain natriuretic peptide (NT-pro-BNP). The study also aimed to define the role of thromboembolic pulmonary artery (PA) obstruction in its etiology. Forty sickle cell disease and 30 thalassemia patients [15 beta-thalassemia major (beta-TM) and 15 beta-thalassemia intermedia (beta-TI)] were screened for PH defined as tricuspid regurgitant velocity (TRV) >2.5 m/sec and evaluated for PA obstruction using ventilation-perfusion lung scan (V/Q), together with measurement of their plasma levels of NT-pro-BNP. Patients were prospectively followed up for a mean of 18 +/- 6.1 months. The prevalence of PH was 37.5, 40.0 and 26.7% in sickle cell disease, beta-TI and beta-TM patients, respectively. Pulmonary hypertension patients were older, had longer disease duration, higher serum ferritin, serum lactate dehydrogenase (LDH) and NT-pro-BNP with lower hemoglobin (Hb) levels compared to patients without PH. N-terminal pro-BNP was positively correlated with duration of illness, TRV, LDH, serum ferritin, and negatively correlated with Hb levels. The strongest predictor for TRV was serum ferritin followed by the NT-pro-BNP level. Forty-six-point-seven percent of sickle cell disease patients with PH had either high or intermediate probability V/Q scan results compared to 10% of thalassemic patients with PH who had high probability V/Q scan results. Pulmonary hypertension is highly prevalent in young sickle cell disease and thalassemia patients, where elevated serum ferritin and NT-pro-BNP are the main indicators.

Magnetic resonance imaging evaluation of mandibular condyle bone marrow and temporomandibular joint disc signal intensity in anaemia patients

OBJECTIVES

To compare the signal intensity (SI) of mandibular condyle bone marrow (MCBM) and the temporomandibular joint (TMJ) disc in patients with chronic anaemia and healthy subjects, and to investigate the relationships between bone marrow changes, age, types of anaemia and severity of anaemia.

METHODS

MRIs of 18 patients with chronic anaemia were compared with those of 12 healthy subjects. The SI of MCBM and the TMJ disc were quantitatively evaluated. The SI of the grey matter (GM), white matter (WM) and the lateral pterygoid muscle were also investigated. Relationships between age, MCBM and TMJ disc signal-intensities and anaemia severity, and correlations between the groups, were analysed.

RESULTS

The mean MCBM SI was lower in anaemia patients (including both subgroups and also separately) than in healthy subjects (P < 0.05). No statistical significance was found for GM, WM and the muscle SI between the anaemia patients and healthy patient group (P > 0.05). No statistical significance was found between the groups with respect to the anterior band, whereas the mean SI value of the posterior band in the study group was significantly lower than in healthy subjects (P < 0.05). There were no correlations between age and MCBM SI, or between anaemia severity and MCBM SI.

CONCLUSIONS

Anaemia may cause bone marrow alterations without any internal derangement. Patients with chronic anaemia exhibit lower mandibular condyle bone marrow and posterior band SI than healthy subjects.

Cardiac function and iron chelation in thalassemia major and intermedia: a review of the underlying pathophysiology and approach to chelation management

Heart disease is the leading cause of mortality and one of the main causes of morbidity in beta-thalassemia. Patients with homozygous thalassemia may have either a severe phenotype which is usually transfusion dependent or a milder form that is thalassemia intermedia. The two main factors that determine cardiac disease in homozygous β thalassemia are the high output state that results from chronic tissue hypoxia, hypoxia-induced compensatory reactions and iron overload. The high output state playing a major role in thalassaemia intermedia and the iron load being more significant in the major form. Arrhythmias, vascular involvement that leads to an increased pulmonary vascular resistance and an increased systemic vascular stiffness and valvular abnormalities also contribute to the cardiac dysfunction in varying degrees according to the severity of the phenotype. Endocrine abnormalities, infections, renal function and medications can also play a role in the overall cardiac function. For thalassaemia major, regular and adequate blood transfusions and iron chelation therapy are the mainstays of management. The approach to thalassaemia intermedia, today, is aimed at monitoring for complications and initiating, timely, regular transfusions and/or iron chelation therapy. Once the patients are on transfusions, then they should be managed in the same way as the thalassaemia major patients. If cardiac manifestations of dysfunction are present in either form of thalassaemia, high pre transfusion Hb levels need to be maintained in order to reduce cardiac output and appropriate intensive chelation therapy needs to be instituted. In general recommendations on chelation, today, are usually made according to the Cardiac Magnetic Resonance findings, if available. With the advances in the latter technology and the ability to tailor chelation therapy according to the MRI findings as well as the availability of three iron chelators, together with increasing the transfusions as need, it is hoped that the incidence of cardiac dysfunction in these syndromes will be markedly reduced. This of course depends very much on the attention to detail with the monitoring and the cooperation of the patient with both the recommended investigations and the prescribed chelation.

Pseudoxanthoma elasticum: genetics, clinical manifestations and therapeutic approaches

Pseudoxanthoma elasticum (PXE) is an inherited disorder that is associated with accumulation of mineralized and fragmented elastic fibers in the skin, vascular walls, and Bruch's membrane in the eye. Clinically, patients exhibit characteristic lesions of the posterior segment of the eye including peau d'orange, angioid streaks, and choroidal neovascularisations, of the skin including soft, ivory-colored papules in a reticular pattern that predominantly affect the neck and large flexor surfaces, and of the cardiovascular system with peripheral and coronary arterial occlusive disease as well as gastrointestinal bleedings. There is yet no definitive therapy. Recent studies suggest that PXE is inherited almost exclusively as an autosomal recessive trait. Its prevalence has been estimated to be 1:25,000-100,000. Very recently, the ABCC6 gene on chromosome 16p13.1 was found to be associated with the disease. Mutations within ABCC6 cause reduced or absent transmembraneous transport that leads to accumulation of extracellular material. Presumably, this mechanism causes calcification of elastic fibers. Despite the characteristic clinical features, the variability in phenotypic expressions, and the low prevalence may be responsible for the disease being underdiagnosed. This review compiles and summarizes current knowledge of PXE pathogenesis and clinical findings. Furthermore, different therapeutic strategies to treat retinal manifestations are discussed, including thermal laser coagulation, photodynamic therapy, and intravitreal injections of drugs inhibiting vascular endothelial growth factor.

Cardiac involvement in sickle beta-thalassemia

Cardiovascular involvement is a leading cause of mortality and morbidity in patients with inherited hemoglobinopathies, but it has not been adequately assessed in sickle beta-thalassemia. We evaluated 115 sickle beta-thalassemia patients, aged 34 +/- 14 years, along with 50 healthy controls, by resting echocardiography. Patients with systolic left ventricular (LV) dysfunction or severe pulmonary hypertension (PHT) also underwent left and right cardiac catheterization and cardiac magnetic resonance imaging (CMR). Left and right chamber dimensions, LV mass, and cardiac index were significantly higher in patients compared to controls (p < 0.001 in most cases). Three patients (2.9%) had reduced LV ejection fraction (<55%); mean LV ejection fraction was significantly lower in patients (p < 0.001). Left and right ventricular systolic tissue Doppler indices and LV diastolic tissue Doppler indices were also impaired in patients. All three patients with systolic LV dysfunction had normal coronary arteries and mild myocardial iron load (CMR T2* values, 18-25 ms). Systolic pulmonary artery pressure was significantly higher in patients compared to controls (p = 0.002); PHT was present in 28 patients (27%), while severe PHT in three (2.9%). In three patients with severe PHT, only one had impaired LV ejection fraction and increased pulmonary wedge pressure. Overall, three patients (2.9%) had a history of heart failure, two with systolic LV dysfunction, and one with severe PHT. Cardiac involvement in sickle beta-thalassemia concerns biventricular dilatation and dysfunction along with PHT, leading to congestive heart failure.

Pulmonary hypertension in a case of Hb-Mainz hemolytic anemia

The development of pulmonary arterial hypertension (PAH) is the leading cause of mortality in patients with thalassemia and sickle cell anemia and was reported to occur in hemolytic anemias such as hereditary stomatocytosis, and paroxysmal nocturnal hemoglobinuria. Here, we report for the first time on the development of PAH in a patient with Hb-Mainz hemolytic anemia. Hb-Mainz is an unstable hemoglobin variant resulting from mutations at codon 98 of the beta chain gene (Val>Glu) characterized by severe chronic hemolytic anemia. The development of PAH in this patient further supports the contention that there is a clinical syndrome of hemolysis-associated development of PAH.

Pulmonary hypertension in beta-thalassemia

Cardiac involvement represents the leading cause of mortality in both forms of beta-thalassemia, namely, thalassemia major (TM) and thalassemia intermedia (TI), and pulmonary hypertension (PHT) is part of the cardiopulmonary complications of the disease. PHT was initially documented in a small group of TI patients with right heart failure. In a subsequent study of a large 110-patient series, aged 32.5 +/- 11.4 years, age-related PHT was encountered in nearly 60% of cases, having caused right heart failure in six of them; interestingly, all patients had preserved left ventricular systolic function. Conflicted evidence, however, existed with respect to the development of PHT in heterogeneously treated and young TM populations. To resolve this discrepancy, a recent study compared cardiac disease between two large aged-matched groups of TM (n = 131) and TI (n = 74) patients, both treated uniformly in the currently accepted manner (regular transfusion and chelation therapy in TM, absence of any particular treatment in TI); well-treated TM patients, in contrast to TI patients, did not develop PHT, while systolic left ventricular dysfunction was present only in TM cases. PHT in beta-thalassemia results from a rather complex pathophysiology, in which chronic tissue hypoxia seems to hold a key role. Although both forms of the disease share a common molecular background, the diverse severity of the genetic defect and of the resulting clinical phenotype require a different therapeutic approach. Regular lifelong therapy in TM patients eliminates chronic hypoxia, thereby preventing PHT, whereas the absence of systematic treatment in TI leads to a cascade of reactions that compensate for chronic anemia, but at the same time allow the development of PHT.

Endothelial function and arterial stiffness in sickle-thalassemia patients

BACKGROUND

Homozygous sickle-cell anemia and beta-thalassemia are characterized by impaired endothelial function, while data on arterial stiffness have hitherto been conflicting. We sought to investigate aortic elastic properties and endothelial function in sickle-thalassemia, which combines molecular and clinical features of the above conditions.

METHODS AND RESULTS

Forty-seven sickle-thalassemia patients, younger than 45 years, with preserved left ventricular (LV) function and no history of smoking, systemic or pulmonary hypertension, diabetes mellitus, dyslipidemia or thyroid disease, along with 40 healthy controls were studied. Aortic strain, distensibility and stiffness index were calculated by echocardiographically-obtained aortic root diameters. Brachial artery endothelial function was assessed by ultrasonographic evaluation of flow-mediated dilatation (FMD) and nitrate-mediated dilatation (NMD). Left ventricle was assessed by echocardiography. Patients had an impaired FMD (4.2+/-2.9% versus 9.2+/-3.8% in controls, p<0.001) with a preserved NMD (16.9+/-5.6% versus 15.2+/-4.8% in controls, p>0.05). Aortic strain and distensibility were lower and aortic stiffness index was higher in patients compared to controls (8.1+/-4.6 versus 5.8+/-2.9, p<0.01). Indexed LV diameters and mass were higher in patients. Systolic LV function was preserved, while 14.9% of patients had an impaired relaxation transmitral inflow pattern. Patients' LV mass index and diastolic mitral E wave deceleration time were positively correlated with aortic stiffness index (p<0.001).

CONCLUSION

Sickle-thalassemia is characterized by a complex vasculopathy, consisting of endothelial dysfunction and increased arterial stiffness, with a global effect on cardiovascular function.

Postnatal alterations in elastic fiber organization precede resistance artery narrowing in SHR

Resistance artery narrowing and stiffening are key elements in the pathogenesis of essential hypertension, but their origin is not completely understood. In mesenteric resistance arteries (MRA) from spontaneously hypertensive rats (SHR), we have shown that inward remodeling is associated with abnormal elastic fiber organization, leading to smaller fenestrae in the internal elastic lamina. Our current aim is to determine whether this alteration is an early event that precedes vessel narrowing, or if elastic fiber reorganization in SHR arteries occurs because of the remodeling process itself. Using MRA from 10-day-old, 30-day-old, and 6-mo-old SHR and normotensive Wistar Kyoto rats, we investigated the time course of the development of structural and mechanical alterations (pressure myography), elastic fiber organization (confocal microscopy), and amount of elastin (radioimmunoassay for desmosine) and collagen (picrosirius red). SHR MRA had an impairment of fenestrae enlargement during the first month of life. In 30-day-old SHR, smaller fenestrae and more packed elastic fibers in the internal elastic lamina were paralleled by increased wall stiffness. Collagen and elastin levels were unaltered at this age. MRA from 6-mo-old SHR also had smaller fenestrae and a denser network of adventitial elastic fibers, accompanied by increased collagen content and vessel narrowing. At this age, elastase digestion was less effective in SHR MRA, suggesting a lower susceptibility of elastic fibers to enzymatic degradation. These data suggest that abnormal elastic fiber deposition in SHR increases resistance artery stiffness at an early age, which might participate in vessel narrowing later in life.

Elastic fibres and vascular structure in hypertension

Blood vessels are dynamic structures composed of cells and extracellular matrix (ECM), which are in continuous cross-talk with each other. Thus, cellular changes in phenotype or in proliferation/death rate affect ECM synthesis. In turn, ECM elements not only provide the structural framework for vascular cells, but they also modulate cellular function through specific receptors. These ECM-cell interactions, together with neurotransmitters, hormones and the mechanical forces imposed by the heart, modulate the structural organization of the vascular wall. It is not surprising that pathological states related to alterations in the nervous, humoral or haemodynamic environment-such as hypertension-are associated with vascular wall remodeling, which, in the end, is deleterious for cardiovascular function. However, the question remains whether these structural alterations are simply a consequence of the disease or if there are early cellular or ECM alterations-determined either genetically or by environmental factors-that can predispose to vascular remodeling independent of hypertension. Elastic fibres might be key elements in the pathophysiology of hypertensive vascular remodeling. In addition to the well known effects of hypertension on elastic fibre fatigue and accelerated degradation, leading to loss of arterial wall resilience, recent investigations have highlighted new roles for individual components of elastic fibres and their degradation products. These elements can act as signal transducers and regulate cellular proliferation, migration, phenotype, and ECM degradation. In this paper, we review current knowledge regarding components of elastic fibres and discuss their possible pathomechanistic associations with vascular structural abnormalities and with hypertension development or progression.

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.