Subclinical parvovirus B19 infection in children with sickle cell anemia.

PURPOSE: To investigate the prevalence and clinical consequences of previous parvovirus B19 exposure in a large cohort of pediatric patients with sickle cell anemia (SCA). METHODS: Prospective serologic testing for previous parvovirus B19 exposure was performed in steady-state pediatric patients with SCA, either prior to starting hydroxyurea therapy or in preparation for transition to the adult service. A retrospective chart review was performed to ascertain whether patients had a documented history of a transient aplastic crisis. RESULTS: The prevalence of serologic evidence of previous parvovirus infection increased with age. The overall prevalence in 102 children with SCA was 53%, ranging from 44% between 5 and 9 years of age to 71% between 17 and 21 years of age. Only 27% of patients had a previous clinically recognized transient aplastic crisis. CONCLUSIONS: By the teenage years, most pediatric patients with SCA have serologic evidence of previous parvovirus B19 exposure. However, subclinical parvovirus infection appears to be common in children with SCA, since most patients have no documented previous transient aplastic crisis.

Sustained long-term hematologic efficacy of hydroxyurea at maximum tolerated dose in children with sickle cell disease.

Hydroxyurea improves hematologic parameters for children with sickle cell disease (SCD), but its long-term efficacy at maximum tolerated dose (MTD) has not been determined. Between 1995 and 2002, hydroxyurea therapy was initiated for 122 pediatric patients with SCD including 106 with homozygous sickle cell anemia (HbSS), 7 with sickle hemoglobin C (HbSC), 7 with sickle/beta-thalassemia (HbS/ beta-thalassemia [6 HbS/beta0, 1 HbS/beta+]), and 2 with sickle hemoglobin OArab (HbS/OArab). Median age at initiation of therapy was 11.1 years. Hydroxyurea was escalated to MTD, with an average dose of 25.4 +/- 5.4 mg/kg per day; the average duration of hydroxyurea therapy has been 45 +/- 24 months (range, 6-101 months). Hydroxyurea was discontinued for 15 (12%) children with poor compliance. Mild transient neutropenia occurred, but no hepatic or renal toxicity was noted. Hydroxyurea therapy led to significant increases in hemoglobin level, mean corpuscular volume, and fetal hemoglobin (HbF) level, whereas significant decreases occurred in reticulocyte, white blood cell, and platelet counts and serum bilirubin levels. Children with variant SCD genotypes also had hematologic responses to hydroxyurea. HbF induction has been sustained for up to 8 years without adverse effects on growth or increased numbers of acquired DNA mutations. Long-term hydroxyurea therapy at MTD is well tolerated by pediatric patients with SCD and has sustained hematologic efficacy with apparent long-term safety.

Prevention of secondary stroke and resolution of transfusional iron overload in children with sickle cell anemia using hydroxyurea and phlebotomy.

OBJECTIVE: Transfusions prevent secondary stroke in children with sickle cell anemia (SCA) but also cause iron overload. Alternatives for stroke prophylaxis with effective therapy to reduce iron burden are needed. STUDY DESIGN: For 35 children with SCA and stroke, transfusions were prospectively discontinued. Hydroxyurea was prescribed for stroke prophylaxis, and phlebotomy removed excess iron. Initial patients discontinued transfusions before hydroxyurea therapy, but later patients overlapped transfusions with hydroxyurea until tolerating full-dose therapy. RESULTS: Children received hydroxyurea for 42 +/- 30 months (range, 3-104 months). Hydroxyurea (26.7 +/- 4.8 mg/kg per day) led to mild neutropenia (3.9 +/- 2.3 x 10(9)/L) with significant increases in hemoglobin concentration, mean corpuscular volume, and fetal hemoglobin. Stroke recurrence rate was 5.7 events per 100 patient-years, but children receiving overlapping hydroxyurea therapy had only 3.6 events per 100 patient-years. For 26 children with >6 months of phlebotomy, 14,311 +/- 12,459 mL blood (315 +/- 214 mL/kg) was removed, with serum ferritin decreasing from a median of 2722 to 298 ng/mL. Among patients completing phlebotomy, liver biopsy documented normal histology and no excess iron deposition. CONCLUSIONS: For children with SCA and stroke, hydroxyurea effectively prevents secondary stroke and serial phlebotomy leads to complete resolution of transfusional iron overload.