We describe a 17-day-old newborn with fever and peripheral blood lymphocytosis. The circulating lymphocytes were large with lobulated and nucleolated nuclei. Their immature and uniform appearance raised the possibility of malignant lymphoma in the leukemic phase. Immunophenotypic study, however, showed that the lymphocytes were CD19^sup +^ B cells with expression of both κ and λ light chains. Molecular biology study confirmed a polyclonal nature of the immunoglobulin heavy-chain gene. Cytogenetic analysis showed a normal karyotype, and viral cultures and serologic studies yielded negative results. The polyclonal lymphocytosis was self-limiting and disappeared within a month.
(Arch Pathol Lab Med. 2005;129:251-252)
Persistent polyclonal B-cell lymphocytosis is a rare disorder that occurs predominantly in women and is characterized by circulating, proliferated polyclonal binucleated B cells.1 This is a benign condition with a chronic and stable clinical course. Reactive lymphocytosis in children is not uncommon and is almost always due to polyclonal CD8^sup +^ T-cell response toward viral infections.23 In this report, we describe an unusual example of polyclonal B-cell lymphocytosis that occurred in a newborn.
REPORT OF A CASE
A 17-day-old male newborn who was born full term by normal delivery presented with fever for 1 day. There was a history of neonatal jaundice (serum bilirubin level up to 13.2 mg/dL) managed by phototherapy. Clinical examination showed a febrile newborn with no rash, lymphadenopathy, or organomegaly. Peripheral blood examination showed the following values: hemoglobin, 13.5 g/dL; platelets, 480 000/µL and leukocytes, 22600/µL. A manual differential cell count revealed 19% neutrophils, 37% lymphocytes, 4% monocytes, 2% eosinophils, and 38% atypical mononuclear cells. The atypical mononuclear cells were large (2 to 3 times the size of a small lymphocyte) and had irregularly folded to tabulated nuclei, open to partially clumped chromatin, distinct nucleoli, and lightly basophilic agranular cytoplasm (Figures 1 and 2). Bone marrow examination showed a normocellular marrow with adequate megakaryocytes, normoblastic erythropoiesis, normal granulopoiesis, and the presence of 12% abnormal mononuclear cells similar to those observed in the peripheral blood. Immunophenotypic study using the labeled streptavidinbiotin technique on cytospin preparation of Ficoll-concentrated mononuclear cells showed that the circulating abnormal mononuclear cells were B cells, expressing CD19 and CD20 but not CDS, CDS, CD10, CD23, and CD56. These B cells showed polytypic staining for κ and λ light chains. The CD3/CD19 ratio was 1:2, and the CD3^sup +^ cells were almost invariably small lymphocytes. Cytogenetic analysis performed by fluorodeoxyuridine-synchronized unstimulated and 12-O-tetradecanoylphorbol-13-acetate stimulated cultures of the marrow mononuclear cells showed a normal karyotype of 46,XY. Polymerase chain reaction using primers against immunoglobulin heavy-chain gene (framework 2 and framework 3) showed a polyclonal pattern. Viral cultures of cerebrospinal fluid, urine, and upper respiratory tract secretions and serologic studies for Epstein-Barr virus, respiratory syncytial virus, influenza virus, parainfluenza virus, adenovirus, cytomegalovirus, herpes simplex virus, and varicella-zoster virus were all negative. Microbiologie culture of the blood was also negative. The patient was treated empirically with ampicillin and gentamycin. His fever subsided 1 day after initiation of antibiotic therapy, and the lymphocytosis gradually disappeared within a month.
Reactive lymphocytosis is common in children during viral infections.2 A notable example is the atypical lymphocytosis associated with infectious mononucleosis. In infectious mononucleosis, the Epstein-Barr virus primarily infects B lymphocytes. During the first week of illness, the infected B lymphocytes proliferate but constitute only 1% to 2% of the peripheral blood lymphocytes. Subsequently, CD8^sup +^ T lymphocytes are produced to control the B-lymphocyte response, and they account for the bulk of circulating atypical lymphocytes characteristic of infectious mononucleosis.3 In fact, it has been shown that all cases of atypical lymphocytosis, irrespective of etiology, are characterized by a marked increase of activated CD8^sup +^ T lymphocytes in the peripheral blood with no increase in B lymphocytes.4 The activated T lymphocytes often show a marked degree of morphologic pleomorphism, which has led Downey to categorize the atypical lymphocytes of infectious mononucleosis into different subtypes.5
In this report, we describe a transient reactive lymphocytosis of unknown etiology in an infant. The circulating proliferated lymphocytes have more irregular and segmented nuclei than the Downey type III cells.s Their morphologic features are alarming in that they exhibit an immature or open chromatin pattern and marked nuclear foldings, raising the possibility of lymphoma because of the atypia. The cytologie features are not in keeping with acute lymphoblastic leukemia or acute myeloid leukemia. It is understandable that lymphoid neoplasms other than lymphoblastic type are extremely rare in this age group, but anaplastic large cell lymphoma and large B-cell lymphoma are certainly possible.6 On immunophenotyping, the atypical lymphocytes are surprisingly shown to represent B rather than T cells. The polytypic pattern of immunoglobulin staining suggests a reactive process, a fact further confirmed by the lack of clonal population on polymerase chain reaction analysis of immunoglobulin genes, absence of cytogenetic abnormality, and clinical evolution. Persistent polyclonal B lymphocytosis is an uncommon disorder that occurs almost exclusively in female patients, usually cigarette smokers, and is characterized by a stable but persistent expansion of polyclonal binucleated CD5^sup -^CD23^sup -^ lymphocytes and elevated serum IgM levels.1 An association with HLA-DR7 phenotype and multiple bcl-2-immunoglobulin gene rearrangements has been previously reported.7 This condition has not been described in children and is certainly different from the case described herein.
To the best of our knowledge, only a single case of polyclonal B-cell lymphocytosis has been reported in an infant.8 In that case, the abnormal lymphocytes were mature CD23^sup +^ HC2^sup +^ B lymphocyte with a single small nucleus and condensed chromatin and scanty cytoplasm, thus making it morphologically different from our case. The association with a febrile illness and the transient nature of the lymphocytosis suggest a viral etiology, although the cause remains elusive despite exhaustive virologie studies.
1. Mossafa H, Malaure H, Maynadie M, et al. Persistent polyclonal B lymphocytosis with binucleated lymphocytes: a study of 25 cases. Br J Haematol. 1999;104:486-493.
2. Jandl JH, ed. Blood: Textbook of Hematology. Boston, Mass: Little Brown & Co; 1987:540-541.
3. Callan MF, Steven N, Krausa P, et al. Large clonal expansions of CD8+ T cells in acute infectious mononucleosis. Nat Med. 1996;2:906-911.
4. Hudnall SD, Patel J, Schwab H, Martinez J. Comparative immunophenotypic features of EBV-positive and EBV-negative atypical lymphocytosis. Cytometry. 2003;55:22-28.
5. Wintrobe MM, Lee GR, Boggs DR, et al. Clinical Hematology. 8th ed. Philadelphia, Pa: Lea & Febiger; 1981: color plate IV.
6. Jaffe ES, Harris NL, Stein H, Vardiman IW, eds. Pathology and Genetics of Tumours of the Haematopoietic and Lymphoid Tissues. Lyon, France: IARC Press; 2001. World Health Organization Classification of Tumours; vol 3.
7. Delage R, Jacques L, Massinga-Loembe M, et al. Persistent polyclonal B-cell lymphocytosis: further evidence for a genetic disorder associated with B-cell abnormalities. Br J Haematol. 2001 ;114:666-670.
8. Gomez P, Matutes E, Sanchez J, et al. An unusual form of persistent polyclonal B lymphocytosis in an infant. Br J Haematol. 2000;110:430-433.
Kit Fai Wong, MD; Hui Leung Yuen, MBBS; Jennifer N. S. Leung, MBBS; John K. C. Chan, MBBS
Accepted for publication September 9, 2004.
From the Departments of Pathology (Drs Wong, Leung, and Chan) and Pediatrics (Dr Yuen), Queen Elizabeth Hospital, Hong Kong SAR, China.
The authors have no relevant financial interest in the products or companies described in this article.
Reprints: Kit Fai Wong, MD, Department of Pathology, Queen Elizabeth Hospital, 30 Cascoigne Rd, Kowloon, Hong Kong SAR, China (e-mail: email@example.com).
Copyright College of American Pathologists Feb 2005
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