SHORT REPORT

Massive expansion of EBV+ monoclonal T cells with CD5 down regulation in EBV-associated haemophagocytic lymphohistiocytosis

Ming-Tsan Lin^1,2, Hui-Mei Chang³, Chang-Jen Huang⁴, Woan-Ling Chen¹, Chi-Yung Lin, Ching-Yang Lin^1,5 and Shih-Sung Chuang⁶

¹ Department of Pediatrics, Changhua Christian Hospital, Changhua, Taiwan
² National Cheng-Kung University Medical School, Tainan, Taiwan
³ Department of Pathology, Changhua Christian Hospital, Changhua, Taiwan
⁴ Institue of Biological Chemistry, Academia Sinica, Taipei, Taiwan
⁵ Department of Clinical Pathology, Changhua Christian Hospital, Changhua, Taiwan; Institute of Medical Research, Chang Jung Christian University, Tainan, Taiwan
⁶ Chi-Mei Medical Centre, Tainan; Taipei Medical University, Taipei, Taiwan

Correspondence to:
Correspondence to:
Dr S-S Chuang
Department of Pathology, Chi-Mei Medical Centre, 901 Chung-Hwa Road, Yung-Kang City, Tainan County 710, Taiwan; cmh5301{at}mail.chimei.org.tw

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 167x10⁹/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 chain gene rearrangement. The patient responded dramatically to intravenous immunoglobulin, interferon 2b, 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.

Abbreviations: EBV, Epstein–Barr virus; HLH, haemophagocytic lymphohistiocytosis; PBMC, peripheral blood mononuclear cell; TCR, T cell receptor; T-LPD, T cell lymphoproliferative disorder

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