[Effect of hydroxyurea on hemoglobin S]

Previous studies have determined the laboratory alterations, clinical efficacy and toxicity profile associated with hydroxyurea (HU) therapy in patients with severe sickle cell anemia. We report the efficacy of HU treatment in the prevention of vaso-occlusive crises in an 11-years-old boy with severe sickle cell disease. The number of vaso-occlusive crises, hospital days and blood transfusions in the year before HU treatment were compared with the same parameters at 6, 12, 24, 36 and 72 months of treatment. A decrease in the frequency of vaso-occlusive crises, blood transfusions and days spent in hospital were demonstrated during the HU treatment period compared to the same period before hand. The clinical and laboratory response to HU was dramatic in this severely affected patient, allowing him a normal schooling and social life. The adverse effects observed were not serious and reversed after transient discontinuation of HU. We conclude that long-term chronic treatment with HU for seriously ill sickle cell patients appears feasible, and devoid of any major toxicity.

Prothrombotic disorders in children with moyamoya syndrome

BACKGROUND AND PURPOSE

Moyamoya syndrome is an uncommon chronic occlusive cerebrovascular disease in children. The origin of moyamoya syndrome remains undetermined. The role of the prothrombotic disorders contributing to its pathogenesis has not been completely elucidated. The purpose of this study was to determine the frequency of prothrombotic disorders in a pediatric population with moyamoya syndrome.

METHODS

From May 1992 to April 2000, a prospective study of 10 consecutive children with moyamoya syndrome was carried out at a single center. Evaluation included the following assays: protein C, protein S, antithrombin, plasminogen, activated protein C resistance, factor V Leiden, and prothrombin gene mutations. Lupus anticoagulant, anticardiolipin antibodies, and anti-beta(2)-glycoprotein I antibodies assays were also performed. The clinical characteristics, underlying diseases, family history of thrombosis, radiological findings, treatment, and outcome were also recorded.

RESULTS

In our series, prothrombotic disorders were detected in 4 patients (40%). Inherited protein S deficiency was found in 1 patient; lupus anticoagulant and anticardiolipin antibodies were detected in the remaining 3 patients. One presented persistent lupus anticoagulant for 2.7 years until his death. In the case of the other 2 patients, 1 has maintained lupus anticoagulant for 9 months, whereas the other has kept anticardiolipin/anti-beta(2)-glycoprotein I antibodies for 10 months.

CONCLUSIONS

We report the hemostatic data of the largest prospective pediatric study carried out at a single center in the western hemisphere. In 4 patients (40%), a prothrombotic disorder was detected. It is tempting to speculate that these hemostatic abnormalities may contribute to the pathogenesis of moyamoya syndrome in some of our patients.

Prothrombotic abnormalities in children with venous thromboembolism

PURPOSE

The aim of this study was to determine the frequency of acquired or inherited prothrombotic disorders in a pediatric population with venous thromboembolism (VTE).

PATIENTS AND METHODS

From May 1992 to April 1998, 56 consecutive children with VTE were prospectively studied at a single center.

RESULTS

The median age was 8.4 years (range, 0.1-18 years). There was a male predominance. Fifty (89%) children had thrombosis in the lower venous system. Risk factors were detected in 54 (96%) children. Twenty-one (38%) thrombotic episodes were related to central venous lines. Family history of thrombosis was positive in 13 (23%) patients. In 26 (46%) patients, a prothrombotic disorder was detected. Nine of them had inherited disorders (protein C deficiency, 5 patients; protein S deficiency, 3 patients; Factor V Leiden mutation, 1 patient), and 13 children had acquired disorders (antiphospholipid antibodies, 5 patients; antithrombin deficiency, 8 patients). The remaining four showed combined abnormalities (Factor V Leiden mutation associated with inherited protein S deficiency, 1 patient; acquired antithrombin deficiency, 2 patients and inherited antithrombin deficiency, 1 patient).

CONCLUSIONS

In the series, a high percentage of prothrombotic disorders was detected; thus, a complete hemostatic evaluation should be performed in all of the children with VTE whether the patients have one or more risk factors.

Prethrombotic disorders in children with arterial ischemic stroke and sinovenous thrombosis

BACKGROUND

Arterial ischemic stroke (AIS) and sinovenous thrombosis (SVT) are relatively rare events in children. The contribution of prethrombotic disorders to the etiology of these entities has not been completely elucidated.

OBJECTIVES

To determine the frequency of inherited and acquired prethrombotic disorders in a pediatric population with AIS and SVT and to report clinical and radiological features.

METHODS

From May 1992 to April 1997, 30 consecutive children with AIS and 10 children with SVT were assisted at a single institution. Hemostatic evaluation was performed for all the children. Evaluation included the following assays: protein C, protein S, antithrombin, plasminogen, activated protein C resistance, factor V Leiden mutation, and the detection of antiphospholipid antibodies. Data concerning baseline demographics, risk factors, presenting features, family history of thrombosis, and radiological findings were also recorded.

RESULTS

One or more prethrombotic disorders were present in 9 children (30%) with AIS (inherited protein S deficiency, 2 patients; inherited protein C deficiency, 1 patient; acquired antithrombin deficiency, 2 patients; antiphospholipid antibodies, 3 patients; and antiphospholipid antibodies and plaminogen deficiency, 1 patient) and in 5 children (50%) with SVT (inherited protein S deficiency, 1 patient; acquired antithrombin deficiency, 3 patients; and antiphospholipid antibodies, 1 patient).

CONCLUSIONS

Most children studied presented both a variety of risk factors for thrombosis and concomitant prethrombotic disorders. Therefore, a complete hemostatic evaluation for all children with AIS and SVT should be performed, despite the presence of obvious clinical risk factors or lack of family history of thrombosis.

Familial idiopathic myelofibrosis and multiple hemangiomas

Idiopathic myelofibrosis (MF) is a rare disease in childhood. The clinical spectrum is very variable. Familial idiopathic MF has been recorded exceptionally. In previous reports idiopathic MF in childhood has been described in association with congenital anomalies and with chromosome abnormalities, although neither of these features have been reported in a familial context. We report two sisters with idiopathic MF and multiple eruptive hemangiomas. Details of their clinical signs, laboratory findings, and histologic features are described.

Molecular characterization of beta-thalassemia genes in an Argentine population

This study was designed to identify the beta-thalassemia mutations in an Argentine population. Seventy-one pediatric patients and 101 available relatives were studied (85 chromosomes). Diagnosis of beta-thalassemia was made by conventional hematological procedures. Molecular studies were carried out by dot-blot and restriction endonuclease analysis on amplified DNA to detect the eight most frequent mutations in the Mediterranean area. We were able to identify 95.3% of the beta-thalassemia mutations in the subjects under study. The four common defects (C-39, 47%; IVS-I nt 110, 22.4%; IVS-I nt 1, 9.4%; and IVS-I nt 6, 5.9%) account for 84.7% of the beta-thalassemia alleles. The alleles and their distributions showed a close similarity to the spectrum of alleles in Italy. The differences might represent the influence of other immigrations, especially from Spain. We conclude that beta-thalassemia in Argentina originated mainly from Italian immigrants. This study will enable us to design an adequate approach to genetic counseling and/or prenatal diagnosis for couples at risk.