title: Massive expansion of EBV+ monoclonal T cells with CD5 down regulation in EBV-associated haemophagocytic lymphohistiocytosis.
abstract: Haemophagocytic lymphohistiocytosis (HLH) comprises primary and secondary forms; the secondary form is most commonly triggered by the Epstein-Barr virus (EBV; EBV-HLH). Patients with EBV-HLH usually exhibit oligoclonal or monoclonal T cell proliferation, which may mimic T cell lymphoproliferative disorder (T-LPD). This article reports on EBV-HLH in a 17-month-old girl with an extreme surge of reactive T lymphocytosis (absolute count 167x10(9)/l) with CD5 down regulation. Bone marrow aspirate and trephine contained florid haemophagocytosis and massive infiltration of CD3+ Epstein-Barr virus-encoded RNA+ lymphocytes, as seen by double labelling. These lymphocytes were monoclonal for EBV and T cell receptor gamma chain gene rearrangement. The patient responded dramatically to intravenous immunoglobulin, interferon alpha2b, ganciclovir and prednisolone, suggesting restoration of her immune system and eradication of the clonal T cells through these immunoregulatory agents. Thus, careful clinicopathological correlation is warranted in the interpretation of immunophenotyping and clonality data in T cell proliferation in association with EBV-HLH to avoid erroneous diagnosis of T-LPD.
authors.affiliation: Department of Pediatrics, Changhua Christian Hospital, Changhua, Taiwan.
authors.forename: Ming-Tsan
authors.initials: MT
authors.lastname: Lin
authors.forename: Hui-Mei
authors.initials: HM
authors.lastname: Chang
authors.forename: Chang-Jen
authors.initials: CJ
authors.lastname: Huang
authors.forename: Woan-Ling
authors.initials: WL
authors.lastname: Chen
authors.forename: Chi-Yung
authors.initials: CY
authors.lastname: Lin
authors.forename: Ching-Yang
authors.initials: CY
authors.lastname: Lin
authors.forename: Shih-Sung
authors.initials: SS
authors.lastname: Chuang
mesh_terms: D018956:CD5 Antigens / Q000378:metabolism*; D003937:Diagnosis, Differential; D015536:Down-Regulation; D020031:Epstein-Barr Virus Infections / Q000150:complications* / Q000276:immunology; D005260:Female; D006801:Humans; D016130:Immunophenotyping; D007223:Infant; D051359:Lymphohistiocytosis, Hemophagocytic / Q000175:diagnosis / Q000276:immunology / Q000821:virology*; D008232:Lymphoproliferative Disorders / Q000175:diagnosis; D016176:T-Lymphocyte Subsets / Q000821:virology*
chemical_list: D018956:CD5 Antigens