Bone health in pediatric transfusion-dependent beta-thalassemia: Circulating osteoprotegerin and RANKL system.

INTRODUCTION: While the mechanism of bone disease in thalassemia is multifactorial and still under investigation, the receptor activator of nuclear factor kappa B (RANK), receptor activator of nuclear factor kappa B ligand (RANKL), and osteoprotegerin (OPG) have pivotal roles in regulating bone metabolism. This study aimed to measure RANKL and OPG serum levels, and to detect the incidence of RANKL rs9533156, OPG rs2073618, and OPG rs2073617 genotypes in pediatric ß-thalassemia patients and to assess their relation to bone mineral density. METHODS: Sixty patients with transfusion-dependent ß-thalassemia (TBT) patients ages 5 to 14 years were included, and 60 healthy, age- and sex-matched volunteers contributed as a control group. The patients were scanned for bone mineral density. RESULTS: The mean of spine dual-energy X-ray absorptiometry (DXA) Z-score in patients was -1.66 ± 1.02 standard deviation (SD). Twenty-four of them had low spine DXA Z-scores. The patients showed significantly lower OPG levels and OPG/RANKLs ratios than the control group (3.28 ± 9.11 ng/ml and 11.38 ± 14.93 ng/ml, and 0.01 ± 0.03 and 0.07 ± 0.09, respectively). The RANKL SNP rs9533156 TC heterozygous genotype was detected more with statistical significance in patients than controls. The incidence of OPG rs2073618 and OPG rs2073617 genotypes were 2.3 times and 1.9 times more frequent in patients than controls, respectively. CONCLUSION: The RANK/RANKL/OPG system may have an important role in regulating bone metabolism in TBT patients, although further studies are needed to clarify its role.

Plasma chitotriosidase and carotid intima-media thickness in children with sickle cell disease.

The relationship between chronic hemolysis with subsequent iron overload, inflammation, and premature atherosclerosis has been documented in hemolytic anemias, particularly ß-thalassemia. However, no such relationship has been established in sickle cell disease (SCD). We sought to evaluate SCD as a risk factor for early vascular insult by measuring carotid intima-media thickness (CIMT) and plasma chitotriosidase and to assess the role of the latter as a potential quantitative indicator of vascular inflammation and atherogenesis. Thirty SCD pediatric patients (3-18 years) and 30 matched controls were enrolled. Full clinical history, with hematological and biochemical parameters, was evaluated. CIMT and chitotriosidase activity were also assessed for all study participants. CIMT values were significantly higher in SCD patients (median 0.42; range 0.32-0.6 mm) compared to controls (0.36; 0.34-0.45 mm), P = 0.03. CIMT correlated positively with age (r = 0.460, P = 0.011), and total number of vascular incidents necessitating hospital admission (r = 0.439, P = 0.015). Similarly, chitotriosidase activity was significantly higher among SCD patients (median 59.6; range 7.3-512 nmol/ml plasma/h) compared to controls (32.7; 6.8-63.1 nmol/ml plasma/h), P < 0.001, and showed a positive correlation with serum ferritin (r = 0.517, P = 0.003) and CIMT (r = 0.535, P = 0.002). SCD children are at risk of developing premature atherogenic changes. Plasma chitotriosidase and CIMT may represent useful predictors of these changes.

13-valent pneumococcal conjugate vaccine (PCV13) is immunogenic and safe in children 6-17 years of age with sickle cell disease previously vaccinated with 23-valent pneumococcal polysaccharide vaccine (PPSV23): Results of a phase 3 study.

BACKGROUND: A large population of older children with sickle cell disease (SCD) is currently vaccinated with only 23-valent pneumococcal polysaccharide vaccine (PPSV23). In immunocompetent adults, PPSV23 vaccination reduces immune responses to subsequent vaccination with a pneumococcal vaccine. The 13-valent pneumococcal conjugate vaccine (PCV13), which addresses this limitation, may offer an advantage to this population at high risk of pneumococcal disease. PROCEDURE: Children with SCD 6-17 years of age previously vaccinated with PPSV23 at least 6 months before study enrollment received two doses of PCV13 6 months apart. Anti-pneumococcal polysaccharide immunoglobulin G (IgG) geometric mean concentrations (GMCs) and opsonophagocytic activity (OPA) geometric mean titers (GMTs) were measured before, 1 month after each administration, and 1 year after the second administration. RESULTS: Following each PCV13 administration, IgG GMCs and OPA GMTs significantly increased, and antibody levels after doses 1 and 2 were generally comparable. Antibody levels declined over the year following dose 2. At 1 year after the second administration, OPA GMTs for all and IgG GMCs for most serotypes remained above pre-vaccination levels. Most adverse events were due to vaso-occlusive crises, a characteristic of the underlying condition of SCD. CONCLUSIONS: Children with SCD who were previously vaccinated with PPSV23 responded well to 1 PCV13 dose, and a second dose did not increase antibody response. PCV13 antibodies persisted above pre-vaccination levels for all serotypes 1 year after dose 2. Children with SCD may benefit from at least one dose of PCV13.