John K Wu

BC Children's Hospital, Vancouver, British Columbia, Canada

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Publications (15)36.88 Total impact

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    ABSTRACT: Congenital thrombotic thrombocytopenic purpura (cTTP) is a rare disorder of childhood that has clinical and laboratory similarities to other, more common conditions. Prompt recognition is required as delays in therapy are associated with significant morbidity and failure to treat may lead to death. While the principles of treatment have not changed, enormous progress in the genetic and molecular understanding has taken place. Emerging treatment options may offer some hope of improved quality of life in future. We describe a Chinese patient with cTTP which resulted from two previously undescribed mutations in the ADAMTS13 gene. Pediatr Blood Cancer 2012; 59: 1296-1298. © 2012 Wiley Periodicals, Inc.
    Pediatric Blood & Cancer 12/2012; 59(7):1296-8. DOI:10.1002/pbc.24159 · 2.56 Impact Factor
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    ABSTRACT: Alpha thalassemia with the absence of 4 α-globin genes leads to fetal hydrops and fetal death from anemia. Historically considered a lethal condition, optimal in utero management of homozygous α-thalassemia is unclear. A fetus of Filipino descent at 26 weeks gestation presented with ultrasound evidence of anemia. Cordocentesis confirmed anemia and homozygous α-thalassemia (--/--). Intrauterine transfusion corrected anemia but fetal growth restriction and oligohydramnios persisted. Intrauterine exchange transfusion improved hemoglobin parameters, fetal growth, and oligohydramnios. The late preterm infant was delivered with classic limb reduction defects. Hemoglobin Bart's is nonfunctional for oxygen transport, and intrauterine exchange transfusion may be effective first-line therapy and further investigation is warranted.
    Journal of Pediatric Hematology/Oncology 12/2011; 33(8):e358-60. DOI:10.1097/MPH.0b013e31821b368c · 0.96 Impact Factor
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    Paediatrics & child health 08/2008; 13(6):507-11. · 1.55 Impact Factor
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    British Journal of Haematology 04/2008; 140(5):589-92. DOI:10.1111/j.1365-2141.2007.06957.x · 4.96 Impact Factor
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    ABSTRACT: Bleeding problems are symptomatic of platelet delta-storage pool diseases (SPDs) such as Hermansky-Pudlak syndrome. Although at present no cure is available for delta-SPD, early diagnosis is of great importance for prophylactic and supportive treatment. This study tested the usefulness of a flow cytometric assay for platelet serotonin in children. The assay was used to diagnose delta-SPD in a 10-year-old girl. Platelet serotonin levels were significantly lower in the patient than in all healthy control subjects (10 children and 10 adults). The serotonin results were supported by traditional tests, which are transmission electron microscopy of whole mounts and adenosine triphosphate release by lumi-aggregometry. The flow cytometric serotonin assay is a major improvement to current pediatric diagnostics. The advantages of this test are small sample volume of fresh or fixed/frozen platelets, availability of objective results within 2 hours of obtaining the blood sample, and automated analysis by flow cytometry.
    American Journal of Clinical Pathology 05/2007; 127(4):626-32. DOI:10.1309/3KRYCPNAPDTVFWGY · 3.01 Impact Factor
  • Journal of Pediatrics 05/2006; 148(4):540-5. DOI:10.1016/j.jpeds.2005.11.024 · 3.74 Impact Factor
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    British Journal of Haematology 08/2005; 130(3):459-460. DOI:10.1111/j.1365-2141.2005.05624.x · 4.96 Impact Factor
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    ABSTRACT: A 3-week-old Caucasian female presented with severe unprovoked parenchymal cerebral haemorrhage. Her plasma factor VII (FVII) activity was <0.01 units/ml. FVII activities for her mother and sister were 0.65 units/ml and 0.51 units/ml, respectively, while her father's level was normal. These results indicated that the mother was heterozygous for a non-functional F7 gene that had also been inherited by the proband's sister. The proband's severe FVII deficiency was caused by a new mutation in her paternal F7 gene coupled with the inheritance of the non-functional maternal F7 gene. DNA sequence analysis revealed that the proband had apparent homozygosity for a novel single point mutation (g.3907G >A) changing the codon for Glu29 to Lys (E29K); neither parent had the E29K mutation. Because of the unlikelihood that the proband was homozygous for two identical new point mutations, the DNA sequence abnormality was more likely to have arisen from a single mutated gene on one allele and a F7 gene deletion on the other allele. Real time polymerase chain reaction (PCR) analysis confirmed that the proband had inherited a gene deletion that was present in the maternal side of the family. Subsequent clotting assays and real time PCR revealed that the maternal deletion also included the closely linked F10 gene.
    British Journal of Haematology 03/2005; 128(3):380-5. DOI:10.1111/j.1365-2141.2004.05296.x · 4.96 Impact Factor
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    ABSTRACT: Although enoxaparin is used to treat thromboembolism in children, current treatment guidelines are largely extrapolated from adults. The objectives of this study were to determine: i) correlation between enoxaparin dose and anti-factor Xa (anti-Xa) level, ii) intra-patient variability, and iii) whether dose or anti-Xa level is a predictor of outcomes. A retrospective chart review was conducted on all hospitalized patients receiving enoxaparin in a tertiary care pediatric institution. Simple linear regression, coefficient of variation (CV), and Student's t-test were used to analyze the objectives. Eighty treatment courses with interpretable anti-Xa levels were analyzed. Mean patient age was 6.5 years. Mean enoxaparin dose was 1.10 mg/kg q12h. Correlation between initial dosing and anti-Xa level was poor; R(2) = 0.0307 and 0.0237 for patients > 2 months with and without cardiac or renal diseases, respectively. Four out of seven patients ≤ 2 months of age compared to 4/32 patients > 2 months had a CV > 40%. Similarly, 4/12 cardiac patients compared to 4/27 non-cardiac patients had a CV > 40%. Neither dose nor anti-Xa level predicted treatment success or adverse reactions (P > .05). These results suggest a need to reexamine the use of anti-Xa levels for guiding enoxaparin therapy. Further prospective studies are warranted to clarify whether routine or selective anti-Xa monitoring should be recommended in pediatric patients.
    01/2005; 10(1):43-50. DOI:10.5863/1551-6776-10.1.43
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    ABSTRACT: Hyperuricemia developed in 2 children with autoimmune hemolytic anemia with reticulocytopenia at a time of hemolytic crisis. One likely cause of hyperuricemia is the destruction of nucleated RBC precursors by autoantibodies. It is advised that patients with autoimmune hemolytic anemia with reticulocytopenia be examined for hyperuricemia. This might explain the reason for reticulocytopenia and might prevent unnecessary bone marrow procedures. When hyperuricemia is present, supportive therapy might be needed to prevent renal damage.
    American Journal of Clinical Pathology 12/2004; 122(6):849-54. DOI:10.1309/8DXD-VJT9-UN60-YACT · 3.01 Impact Factor
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    ABSTRACT: To evaluate the ability of published dosage guidelines for enoxaparin to achieve therapeutic anticoagulation and to determine whether the routine monitoring of anti-Xa levels is still necessary at a tertiary care pediatric institution. Consecutive charts and laboratory records were reviewed for all patients receiving treatment doses of enoxaparin for thrombosis in the authors institution over a 4-year period (1998-2002). Sixty-six percent (25/38) of the anti-Xa levels were within the recommended therapeutic range (0.5-1.0 [+/- 10%] U/mL) after two doses. The success rates of achieving therapeutic levels were 1/6, 2/3, 6/9, 10/11, and 6/9, for patients 2 months or younger, more than 2 months to 1 year, more than 1 year to 6 years, more than 6 years to 12 years, and more than 12 years of age, respectively. Patients with cardiac or renal disease were more likely to achieve high anti-Xa levels. Thirty-seven percent of patients reported adverse effects. The most common effects were injection site-related bruising and minor bleeding. One patient experienced a major bleed that was not life-threatening. Most patients achieved therapeutic anticoagulation when dosed according to the published guidelines. Children with cardiac conditions or renal insufficiency or those younger than 2 months were more likely to require dosage adjustments to achieve the therapeutic range. Routine monitoring of anti-Xa levels is still necessary in these patient populations, particularly when the early establishment of therapeutic anticoagulation may be critical. Enoxaparin appears to be well tolerated in the authors' patient population.
    Journal of Pediatric Hematology/Oncology 10/2004; 26(9):561-6. DOI:10.1097/01.mph.0000139453.22338.d9 · 0.96 Impact Factor
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    ABSTRACT: Hemorrhagic pseudotumour, also known as organized hematoma, is a rare, benign condition that is locally aggressive. It occurs in 1 to 2% of patients with hemophilia.(1) The clinical presentation and radiologic appearance mimic malignancy, making histologic evaluation necessary for a definitive diagnosis. Of the four previously reported cases of hemorrhagic pseudotumour of the maxillary sinus, systemic coagulopathy was present in only one patient. This report describes a case of a hemorrhagic pseudotumour of the maxillary sinus in a 12-year-old girl with factor II deficiency and recent use of ibuprofen.
    The Journal of otolaryngology 07/2004; 33(3):206-8. DOI:10.2310/7070.2004.03090 · 0.50 Impact Factor
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    ABSTRACT: We describe a complicated genetic counseling and prenatal diagnostic case involving an East Indian couple that had lost two consecutive pregnancies. Hemoglobinopathy screening was conducted to investigate the possibility of Hb Bart's hydrops fetalis or Hb H hydrops fetalis. The initial work-up indicated that alpha-thalassemia was not a contributing factor, with both parents being carriers of single gene deletions (-alpha(3.7)/alphaalpha). However, the Hb electrophoresis results indicated that the couple might be at risk for having children with Hb E/Hb Lepore disease. Subsequent DNA testing demonstrated that the father carried the Hb E mutation, but failed to confirm that the mother carries the Hb Lepore deletion. Sequence analysis revealed that the mother was heterozygous for a common East Indian beta(0)-thalassemia mutation, yet had a normal level of Hb A(2). The mother also carried a previously unreported missense mutation of the delta-globin gene, in cis with the beta(0)-thalassemia mutation, which gave rise to the minor Hb variant originally misidentified as Hb Lepore. This case illustrates the importance of comprehensive molecular analyses for accurate assessment of genetic risks for hemoglobinopathy syndromes.
    American Journal of Hematology 11/2003; 74(3):179-81. DOI:10.1002/ajh.10423 · 3.48 Impact Factor
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    ABSTRACT: Rhabdomyosarcoma is the most common type of soft tissue sarcoma in children. The tumor spreads by local extension, to regional lymph nodes, or by distant metastases. Metastatic spread to the testicle has been rarely described. The authors describe 2 boys who were found to have intratesticular metastases after presenting with primary tumors in their extremities. The first patient, an 11-year-old boy presented with primary disease in his left foot and an enlarged testicle. Rhabdomyosarcoma was found histologically in both the foot and the testicle. A second boy 17 years of age had a primary tumor involving the left upper extremity treated with amputation, chemotherapy, and radiotherapy. A relapse was noted 2 years later in the left testicle and was treated with orchiectomy. The authors discuss the implications and the management of this rare presentation of metastatic rhabdomyosarcoma.
    Journal of Pediatric Surgery 09/2003; 38(8):E1-3. DOI:10.1016/S0022-3468(03)00288-4 · 1.31 Impact Factor
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    ABSTRACT: Currently bone marrow transplantation (BMT) with an HLA-identical sibling donor is recommended as optimal therapy for children with acquired severe aplastic anemia (SAA). Immunosuppressive therapy (IST) has become a very successful initial therapy for SAA in children lacking a related bone marrow donor. We wished to evaluate whether current IST regimens may be as efficacious as BMT. A retrospective review identified children treated for SAA over a 12-year period. Children with a related donor received a BMT. Children lacking a donor were treated with IST followed by a "rescue" BMT if IST was ineffective. IST consisted of anti-thymocyte globulin and steroid +/- cyclosporine A. Transfusion independence and survival rates were compared between the two groups. Twenty-seven children were identified. Nine received a related BMT; seven of these survive and are transfusion independent (median follow-up 54 months). Sixteen of 18 patients who received IST are transfusion-independent survivors, including three of four patients who received a rescue BMT (median follow-up 33.5 months). Actuarial survival is 75% (95% CI = 45%, 105%) and 92% (95% CI = 78%, 107%) for the BMT and IST groups, respectively (p = 0.15). Severe toxicity was not experienced by any patient as a result of IST. Equivalent rates of transfusion independence and survival were experienced by patients receiving BMT and IST. We propose that a prospective trial be undertaken to evaluate IST as initial therapy in all children with SAA, to be followed by BMT if there is inadequate response.
    Journal of Pediatric Hematology/Oncology 01/1997; 19(2):115-23. DOI:10.1097/00043426-199703000-00004 · 0.96 Impact Factor