Unusual Bone Marrow Manifestations of Parvovirus BI9 Infection in Immunocompromised Patients TERRI W. CROOK, MD, BEVERLY BARTON ROGERS, MD, RICHARD D. McFARLAND, PHD, MD, STEVEN H. KROFT, MD, PIETRO MURETTO, MD, JOSE A. HERNANDEZ, MD, M. JANE LATIMER, MD, AND ROBERT W. McKENNA, MD Parvovirus B19 is responsible for a spectrum of disease in humans. The usual bone marrow findings in acute parvovirus infec- tious are marked erythroid hypoplasia and occasional giant erythro- blasts. Intranuclear inclusions in developing erythroid precursors are rarely described in children or adults with parvovirus infection, although abundant intranuclear inclusions are commonly observed in the placenta and other tissues in infected fetuses. In this study, 8 patients are reported in whom the first evidence of parvovirus infection was the recognition of numerous intranuclear inclusions in erythroid precursors on bone marrow biopsy sectious. Six of the 8 patients had documented immunodeficiencies; 4 had acquired im- mune deficiency syndrome (AIDS), and 2 were on chemotherapy. Five of 7 patients were negative for immunoglobulin G (IgG) anti- parvovirus antibodies, including all 4 with AIDS. Unlike the typical pattern in parvovirus infection, the bone marrow was hypercellniar in most of the patients, and erythroid precursors were usually increased with the entire spectrum of normoblast maturation represented; abundant intranuclear inclusions were observed similar to the finding in fetuses. The inclusions were variably eosinophilic and compressed the chromatin against the nuclear membrane. In situ hybridization showed parvovirus B19 DNA in numerous erythroid precursors in all cases. The findings of erythroid maturation and abundant viral inclusions in these immunocompromised patients is consistent with the hypothesis that failure to produce effective IgG parvovirus neutralizing antibodies may lead to persistent infection through viral tolerance that allows erythroid development of infected cells past the pronormoblast stage. Identification of parvovirus inclusions in mar- row biopsies and subsequent confirmation of infection by in situ hybridization can be important in the assessment of anemia in immunodeficient patients because serological studies for parvovirus B19 are frequently negative. Htnu PATI-IOI~ 31:161-168. Copyright © 2000 by W.B. Saunders Company Key words: parvovirus B19, nuclear inclusions, AIDS, immunode- ficient, bone marrow. Abbreviations: AIDS, acquired immune deficiency syndrome; CLL, chronic lymphocytic leukemia; H1V, human immunodeficiency virus; ALL, acute lymphoblastic leukemia; MCV, mean cell volume; TAC, transient aplastic crisis; PCR, polymerase chain reaction; M:E, myeloid-to-erythroid ratio; SSC, sodium chloride sodium citrate; TBS, Tris-buffered saline; Ig, immunoglobulin. Parvovirus B19 infection is responsible for a spec- trum of disease in humans, including hydrops fetalis, erythema infectiosum of childhood (fifth disease), polyarthralgia, and self-limited erythroblastopenia. 1,9 It is also a well-known cause of "aplastic crisis" in patients with chronic hemolytic anemia and of prolonged ery- throid suppression in immunodeficient patients. 34 Typi- cally, the major changes in the bone marrow are marked erythroid hypoplasia and giant proerythro- blasts. 2,9 Intranuclear inclusions are commonly found in hematopoietic cells in tissue sections from infected fetuses, but they are rarely reported in individuals past the fetal period. 1°q3 In this study, the clinical and morphological fea- tures of parvovirus B19 infection in 8 patients with chronic diseases who developed moderate to severe anemia are described. In most of the cases, there were normal or increased numbers of bone marrow ery- throid precursors showing a full spectrum of matura- tion and abundant parvovirus B19 inclusions. From the Department of Pathology, University of Texas Southwest- ern Medical Center, Dallas, TX; and Azienda Ospedaliera "San Salvatore," Pesaro, Italy. Accepted for publication October 7, 1999. Address correspondence to Robert W. McKenna, MD, Depart- ment of Pathology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75235-9072. Copyright © 2000 by W.B. Saunders Company 0046-8177/00/3102-0004510.00/0 MATERIALS AND METHODS Clinical Studies Seven of the patients in this study were diagnosed and treated at The University of Texas Southwestern Medical Center affiliated hospitals and 1 at Azienda Ospedaliera "San Salvatore," Pesaro, Italy. Review of each patient's hospital records was performed retrospectively. Morphological Studies In all cases, Wright-Giemsa-stained peripheral blood and bone marrow aspirate smears and hematoxylin and eosin- stained B5-fixed sections of bone marrow trephine biopsy specimens and aspirate particle sections were studied by light microscopy. In 2 cases (patients 1 and 7), bone marrow trephine biopsy and aspirated marrow particles were exam- ined by electron microscopy. The bone marrow biopsy speci- mens were decalcified and dehydrated in a graded series of ethanol, embedded in eponaryldite, thin sectioned at 70 to 80 nm, stained with uranyl acetate and lead citrate, and exam- ined in aJEOL 1200 transmission electron microscope. The bone marrow particles were selected and cut from the paraffin block, deparaffinized in xylene, fixed in glutaraldehyde and osmium tetroxide, dehydrated, and processed as above. Studies for Identification of Parvovirus B19 Infection In situ hybridization for parvovirus B19 DNA was per- formed at Children's Medical Center of Dallas on all speci- 161