Comment
Prevalence and Presentation
Epstein-Barr virus is a ubiquitous γ-herpesvirus with tropism for B cells, affecting more than 90% of the adult population worldwide. In addition to infecting B cells, EBV is capable of infecting T and NK cells, leading to various EBV-related lymphoproliferative disorders (LPDs). The frequency and clinical presentation of infection varies based on the type of EBV-infected cells and the state of host immunity.1-3
Primary infection usually is asymptomatic and occurs early in life; when symptomatic, the disease usually presents as infectious mononucleosis (IM), characterized by polyclonal expansion of infected B cells and subsequent cytotoxic T-cell response. A diagnosis of EBV infection can be made by testing for specific IgM and IgG antibodies against VCA, early antigens, and EBV nuclear antigen proteins.3,4
Associated LPDs
Although most symptoms associated with IM resolve within weeks or months, persistent or recurrent IM-like symptoms or even lasting disease occasionally occur, particularly in children and young adults. This complication is known as chronic active EBV infection (CAEBV), frequently associated with EBV-infected T-cell or NK-cell proliferation, especially in East Asian populations.3,5
Epstein-Barr virus–positive T-cell and NK-cell LPDs of childhood include CAEBV infection of T-cell and NK-cell types and systemic EBV-positive T-cell lymphoma of childhood. The former includes hydroa vacciniforme–like LPD and severe mosquito bite allergy.3
Systemic EBV-Positive T-cell Lymphoma of Childhood
This entity occurs not only in children but also in adolescents and young adults. A fulminant illness characterized by clonal proliferation of EBV-infected cytotoxic T cells, it can develop shortly after primary EBV infection or is linked to CAEBV infection. The disorder is rare and has a racial predilection for Asian (ie, Japanese, Chinese, Korean) populations and indigenous populations of Mexico and Central and South America.6-8
Complications
Systemic EBV-positive T-cell lymphoma of childhood is often complicated by hemophagocytic syndrome, coagulopathy, sepsis, and multiorgan failure. Other signs and symptoms include high fever, rash, jaundice, diarrhea, pancytopenia, and hepatosplenomegaly. The liver, spleen, lymph nodes, and bone marrow are commonly involved, and the disease can involve skin, the heart, and the lungs.9,10
Diagnosis
When systemic EBV-positive T-cell lymphoma occurs shortly after IM, serology shows low or absent anti-VCA IgM and positive anti-VCA IgG. Infiltrating T cells usually are small and lack cytologic atypia; however, cases with pleomorphic, medium to large lymphoid cells, irregular nuclei, and frequent mitoses have been described. Hemophagocytosis can be seen in the liver, spleen, and bone marrow.3,11
The most typical phenotype of systemic EBV-positive T-cell lymphoma is CD2+CD3+CD8+CD20−CD56−, with expression of the cytotoxic granules known as T-cell intracellular antigen 1 and granzyme B. Rare cases of CD4+ and mixed CD4+/CD8+ phenotypes have been described, usually in the setting of CAEBV infection.3,12 Neoplastic cells have monoclonally rearranged TCR-γ genes and consistent EBER positivity with in situ hybridization.13 A final diagnosis is based on a comprehensive analysis of clinical, morphological, immunohistochemical, and molecular biological aspects.
Clinical Course and Prognosis
Most patients with systemic EBV-positive T-cell lymphoma have an aggressive clinical course with high mortality. In a few cases, patients were reported to respond to a regimen of etoposide and dexamethasone, followed by allogeneic hematopoietic stem cell transplantation.3
In recognition of the aggressive clinical behavior and desire to clearly distinguish systemic EBV-positive T-cell lymphoma from CAEBV infection, the older term systemic EBV-positive T-cell LPD of childhood, which had been introduced in 2008 to the World Health Organization classification, was changed to systemic EBV-positive T-cell lymphoma of childhood in the revised 2016 World Health Organization classification.6,12 However, Kim et al14 reported a case with excellent response to corticosteroid administration, suggesting that systemic EBV-positive T-cell lymphoma of childhood may be more heterogeneous in terms of prognosis.
Our patient presented with acute IM-like symptoms, including high fever, tonsillar enlargement, lymphadenopathy, and hepatosplenomegaly, as well as uncommon oral ulcers and skin lesions, including indurated nodules. Histopathologic changes in the skin nodule, proliferation in bone marrow, immunohistochemical phenotype, and positivity of EBER and TCR-γ monoclonal rearrangement were all consistent with systemic EBV-positive T-cell lymphoma of childhood. The patient was positive for VCA IgG and negative for VCA IgM, compatible with systemic EBV-positive T-cell lymphoma of childhood occurring shortly after IM. Neither pancytopenia, hemophagocytic syndrome, nor multiorgan failure occurred during the course.
Differential Diagnosis
It is important to distinguish IM from systemic EBV-positive T-cell lymphoma of childhood and CAEBV infection. Detection of anti–VCA IgM in the early stage, its disappearance during the clinical course, and appearance of anti-EBV–determined nuclear antigen is useful to distinguish IM from the neoplasms, as systemic EBV-positive T-cell lymphoma of childhood is negative for anti-EBV–determined nuclear antigen. Carefully following the clinical course also is important.3,15
Epstein-Barr virus–associated hemophagocytic lymphohistiocytosis can occur in association with systemic EBV-positive T-cell lymphoma of childhood and might represent a continuum of disease rather than distinct entities.14 The most useful marker for differentiating EBV-associated hemophagocytic lymphohistiocytosis and systemic EBV-positive T-cell lymphoma of childhood is an abnormal karyotype rather than molecular clonality.16
Outcome
Mortality risk in EBV-associated T-cell and NK-cell LPD is not primarily dependent on whether the lesion has progressed to lymphoma but instead is related to associated complications.17
Conclusion
Although systemic EBV-positive T-cell lymphoma of childhood is a rare disorder and has race predilection, dermatologists should be aware due to the aggressive clinical source and poor prognosis. Histopathology and in situ hybridization for EBER and TCR gene rearrangements are critical for final diagnosis. Although rare cases can show temporary resolution, the final outcome of this disease is not optimistic.