الفهرس 
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Abstract
Sickle cell disease has evolved into a debilitating disorder with emerging end-organ damage. Bone involvement is a frequent clinical manifestation of SCD and is a source of chronic, progressive disability, such as the long-term effects on growth, and chronic bone damage in the form of avascular necrosis and osteomyelitis. Osteopenia and osteoporosis are often asymptomatic; however, pain, fractures, deformities, and vertebral collapse may occur and require chronic analgesia, mechanical support, and surgical interventions (Almeida & Roberts 2005; Voskaridou et al. 2006b; Sarrai et al. 2007; Sadat-Ali et al. 2008; Serarslan et al. 2010).
In the current study we aimed to assess BMD status among children with SCD and SCT. We also aimed to determine the level of serum TRACP 5b in this group of
patients and its relation with disease complications, markers of hemolysis, serum ferritin. We also aimed to investigate its role as a predictor of osteoclastic activity in this group of patients.
We conducted the study on 30 patients with SCD and 8 patients with SCT who were recruited from Ain Shams University Pediatric Hematology outpatient clinic, and 32 healthy age and sex matched subjects as a control group. All the studied patients were subjected to detailed medical history including complications of sickle cell disease, clinical examination including anthropometric measurements (weight,
height, and body mass index (BMI)), and routine laboratory testing including complete blood count (CBC), reticulocytic count, serum lactate dehydrogenase (LDH), serum bilirubin,
and serum alkaline phosphatase (ALP). Measurement of serum TRACP 5b was done by ELISA. All patients were subjected to
assessment of bone mineral density using DXA scan with calculation of z-score for bone mineral density. Also patients were assessed for the presence of PHT using echocardiography with assessment of tricuspid regurgitant jet velocity (TRV).
In the present study, the incidence of pulmonary hypertension among SCD patients was 16.7%. Frequent vasoocclusive crisis and acute chest syndrome were found in 26.7% and 20% of patients, respectively. Bone fractures and avascular necrosis were found in 13.3% and 10 % of patients, respectively. Of the studied SCD patients, 66.7% received hydroxyurea and 60% were on chelation therapy. 13.3%of the SCD patients were splenctomized.
Bone mineral density was decreased in SCD patients as compared with SCT and controls while no significant difference was found between the latter 2 groups. SCD patients with abnormal DXA scan had higher age, ferritin and ALP compared with those having normal BMD. The incidence of splenectomy and endocrine complications was higher among
SCD patients with abnormal BMD.
BMD was positively correlated with weight-SDS, height-SDS and body mass index SDS (BMI-SDS) and hemoglobin level while negatively correlated with platelet count and ALP. Both
whole body and lumbar spine BMD were positively correlated.
Serum TRACP 5b was significantly higher in SCD patients than SCT and controls while levels were consistent between traits and controls. Hydroxyurea-treated patients as well as those on chelation therapy had lower TRACP 5b levels than untreated patients although levels did not reach a significant level. TRACP 5b levels were comparable between patients with and without PHT risk. TRACP 5b was positively correlated to lactate dehydrogenase (LDH) while no relation with other variables including serum ferritin, ALP, BMD and TRV.
No significant difference was found between patients with sickle cell anemia or those with sickle thalssemia as regards any of the studied variables including TRACP 5b and BMD.