الفهرس 
Introduction and aim of the workOnly 14 pages are availabe for public view
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Abstract
PB19 is a very small (22 nm) non enveloped virus with a negative single-stranded DNA genome. It is the only member of the family parvoviridae known to be pathogenic in humans. The only natural host cell of PB19 is the human erythroid progenitors. In healthy individuals, the major presentation of PB19 infection is erythema infectiosum. However, in patients with underlying hemolytic disorders, infection is the primary cause of TAC. In immunosuppressed patients, persistent infection may develop that presents as PRCA and chronic anemia. In utero infection may result in hyDROPs fetalis or congenital anemia. Moreover, PB19 infection may be implicated in the development of childhood acute leukaemia (Weir, 2005). This study attempts to confirm the relation between the human PB19 infections as one of the predisposing factors of aplastic crisis in patients with haemolytic anaemias and its association with acute leukaemias. To reach that; we retrospectively investigated 85 pediatric patients selected from the Hematology Out Patient Clinic and inpatient unit of Mansoura University Children’s Hospital. Ten healthy subjects with matched age and sex were included as controls. Patients were classified into five groups. group I included 25 patients with hemolytic anemia in aplastic crisis, group II included 20 patients with hemolytic anemia without aplastic crisis, group III included 20 leukemic patients under chemotherapy, group IV included 20 patients of recently diagnosed acute leukemia and 10 healthy subjects as controls in group V. All patients were subjected to proper history taking, full clinical examination to evaluate the fever, pallor, rash, HSM and LN. Routine laboratory investigations were performed including complete blood count, reticulocytic count, ESR and serum bilirubin (Total & Direct). Serological testing of PB19 antibodies (IgM and IgG) using ELISA were done to all cases and control groups. Detection of PB19 DNA was performed by PCR to 8 patients from the group of hemolytic anemia with aplastic crisis, 18 patients of acute leukemia receiving chemotherapy and 20 patients of recently diagnosed acute leukemia. In the present study; age and gender had insignificant differences among studied groups (P= 0.75, P=0.77 respectively). There was statistically significant difference in the prevalence of PB19 IgM (P= 0.02), IgG (P= 0.01) and PCR (P= 0.004) among studied groups. In group I IgG had the highest positive rate (56%) followed by IgM (36%) and PCR (25%). Also, in group II IgG had the highest positive rate (35%) followed by IgM (5%). This higher prevalence of PB19 IgG antibodies among patients with chronic blood disorders in group I and II mostly due to multiple blood transfusions taken by these patients which play a corner stone in the transmission of the virus. In group III IgG also had the highest positive rate (45%) followed by IgM (35%) and PCR (25%). There may be an association between AL and PB19 infection which results from immunosupression as reported by more than 20 reports. It seems also that repeated blood transfusions to those patients could play a role in such high prevalence of PB19. However, in group IV IgM had the highest positive rate (50%) followed by PCR (45%) then IgG (40%). These findings indicate the pathogenic role of PB19 in hematological disorders of children. In this study; there was statistically significant difference between groups in the occurrence of recent infection and old infection (P<0.001). Recent PB19 infection was diagnosed by positive IgM and/or PCR. Old PB19 infection was diagnosed by positive IgG. In group I and group II old infection had the highest rates (40%, 30% respectively) than recent infection (36%, 5% respectively). from these results we can conclude that recent PB19 infection was the most common cause of TAC in patients with hemolytic anemia. On the other hand; in group III and group IV recent infection had the highest rates (50%, 70% respectively) than old infection (25% for each). In leukemic patients receiving chemotherapy, there was high presentation of recent PB19 infection which may be due to susceptibility of immunocompromised patients to infection. There has been much speculation about the role of PB19 in childhood AL; some hypothesized that it is a risk factor in developing AL which has been suggested that AL may be initiated by an in utero infection of the fetus. Others hypothesized that it has potential effects to precipitate different forms of cytopenia in patients proir to or at the diagnosis of AL. In the present study; we showed the comparison between the effects of recent PB19 infection on blood picture parameters among all patients groups and control group. from those results we observed that the main laboratory findings of recent PB19 infection in our studied groups were anemia (Hb < 9.5 g/dl and P<0.001, RBCs count < 3.2 x 1012/L and P<0.001), neutropenia, lymphocytosis and high ESR (1st hour). Conclusion: Parvovirus B19 is a common, not a rare virus in patients with hematological problems, either hemolytic anemia, recently diagnosed AL or AL under chemotherapy. Parvovirus B19 must be suspected and screened for when there is chronic anemia in those patients associated with neutropenia and lymphocytosis. IgM is a good predictor for the diagnosis of recent infection of parvovirus B19 in immunocompetent patients. Determination of specific cutoff value of parvovirus IgM for each lab seems essential to increase sensitivity and specificity of the serological assay to highlight the cases with true viremia. In immunocompromised patients, presence of IgM indicates acute parvovirus B19 infection, but its absence never excludes the infection. Although ELISA is the cheapest method for diagnosis of parvovirus B19 infection; combined use of ELISA and PCR is necessary for optimal diagnosis of the virus in those patients.