Parvovirus B19 infection in Tunisian patients with sickle-cell anemia and acute erythroblastopenia.

BACKGROUND: Human parvovirus B19 is the etiologic agent of erythema infectiosum in children. It is also associated with other clinical manifestations in different target groups. Patients with chronic hemolytic anemia are at high risk of developing acute erythroblastopenia following infection by the virus. They usually become highly viremic and pose an increased risk of virus transmission. Close monitoring of such high risk groups is required for epidemiologic surveillance and disease prevention activities. Here we report a molecular epidemiological study on B19 virus infection in Tunisian patients with chronic hemolytic anemia. METHODS: This study was conducted on 92 young chronic hemolytic anemia patients who attended the same ward at the National Bone Marrow Transplantation Center of Tunis and 46 controls from a different hospital. Screening for IgM and IgG anti-B19 antibodies was performed using commercially available enzyme immunoassays and B19 DNA was detected by nested PCR in the overlapping VP1/VP2 region. DNA was sequenced using dideoxy-terminator cycle sequencing technology. RESULTS: Anti-parvovirus B19 IgG antibodies were detected in 26 of 46 sickle-cell anemia patients, 18 of 46 beta-thalassemia and 7 of 46 controls. Anti-parvovirus B19 IgM antibodies were detected only in 4 of the sickle-cell anemia patients: two siblings and two unrelated who presented with acute erythroblastopenia at the time of blood collection for this study and had no history of past transfusion. B19 DNA was detected only in sera of these four patients and the corresponding 288 bp nested DNA amplicons were sequenced. The sequences obtained were all identical and phylogenetic analysis showed that they belonged to a new B19 virus strain of Genotype1. CONCLUSION: A new parvovirus B19 strain of genotype1 was detected in four Tunisian patients with sickle-cell anemia. Virus transmission appeared to be nosocomial and resulted in acute erythroblastopenia in the four patients. The possibility of independent transmission of this B19 variant to the patients is unlikely in light of the present epidemiological data. However this possibility cannot be ruled out because of the low genetic variability of the virus.

[Biological diagnosis of Von Willebrand disease and its difficulties]. / Diagnostic biologique de la maladie de Willebrand et ses difficultes.

Von Willebrand disease is the most common inherited bleeding disorder, with autosomal genetic transmission, dominant in most cases. It is due to quantitative and/or qualitative deficiency of Von Willebrand factor, a multimeric complex glycoprotein that plays 2 central roles in hemostasis, since it is implicated in adhesion and aggregation of platelets under conditions of high shear forces and acts as a carrier for coagulation factor VIII in plasma. Clinically, this disease is mostly characterized by mucocutaneous bleeding and marked clinical heterogeneity, even in the same family, going from severe to uncouth forms or even asymptomatic. Laboratory diagnosis is based on 3 levels of hemostasis testing. Screening tests making suspicion of the disease, must be completed by specific assays to estabilish the diagnosis. Discriminating tests allow accurate characterization of the numerous types and subtypes of the disease, a crucial step to adapt therapeutics. The classification based on the accumulating knowledge of the different phenotypes, differentiate between quantitative (types 1 and 3) and qualitative deficiencies (types 2). Von Willebrand disease's diagnosis is not, often easy. In fact, several technical or genetic factors and different physiopathological circumstances interfere in the interpretation of explorations results and cause diagnostic difficulties that will be discussed.

[Leg ulcer in a patient treated with hydroxyurea for polycythemia vera]. / Ulcère de jambe chez une malade traitée par hydroxyurée pour maladie de Vaquez.

INTRODUCTION: Causes of leg ulcers vary widely, although venous insufficiency and peripheral arteriopathy are most common. Ulcers are much rarer in patients treated by hydroxyurea. CASE: A 66-year-old woman who had been treated with hydroxyurea for polycythemia vera for four years came to our consultation a month after ulceration of the left lateral malleolus had begun. Symmetric peripheral pulses were present and there was no patent venous insufficiency. After two months of local symptomatic treatment, the size of the ulcer had increased. The possible involvement of hydroxyurea in the genesis and maintenance of this leg ulcer was then considered. Hydroxyurea was stopped, and the ulcer progressively grew smaller, finally healing completely two months later. DISCUSSION: We conclude that hydroxyurea was the primary cause of the malleolar ulcer, for it healed rapidly when this treatment stopped. Hydroxyurea causes cutaneous atrophy; when followed by microtrauma, associated with deterioration in DNA repair mechanisms, it may lead to the formation of persistent cutaneous ulcers. Hydroxyurea can also affect the microcirculation and induce tissular anoxia, which may also explain both the occurrence of cutaneous ulcers after microtrauma and their often painful character.