Dual respiratory virus detection in adult patients with acute respiratory illness.

BACKGROUND: Nonrandom multiple respiratory virus (RV) detection provides evidence for viral interference among respiratory viruses. However, little is known as to whether it occurs randomly. METHODS: The prevalence of dual RV detection (DRVD) in patients with acute respiratory illnesses (ARIs) at 4 academic medical centers was investigated; data about the prevalence of 8 RVs were collected from the Korean national RV surveillance dataset. Linear regression analysis was performed to assess the correlation between observed and estimated prevalence of each type of DRVD. RESULTS: In total, 108 patients with ARIs showing DRVD were included in this study between 2011 and 2017. In several types of regression analysis, a strong correlation was observed between the observed and estimated prevalence of each type of DRVD. Excluding three DRVD types (influenza/picornavirus, influenza/human metapneumovirus, and adenovirus/respiratory syncytial virus), the slope of the regression line was higher than that of the line of random occurrence (1.231 > 1.000) and the 95% confidence interval of the regression line was located above the line of random occurrence. CONCLUSIONS: Contrary to the results of previous epidemiologic studies, most types of DRVD occur more frequently than expected from the prevalence rates of individual RV, except for three underrepresented pairs above.

Machine-Learning-Based Approach to Differential Diagnosis in Tuberculous and Viral Meningitis.

BACKGROUND: Tuberculous meningitis (TBM) is the most severe form of tuberculosis, but differentiating between the diagnosis of TBM and viral meningitis (VM) is difficult. Thus, we have developed machine-learning modules for differentiating TBM from VM. MATERIAL AND METHODS: For the training data, confirmed or probable TBM and confirmed VM cases were retrospectively collected from five teaching hospitals in Korea between January 2000 - July 2018. Various machine-learning algorithms were used for training. The machine-learning algorithms were tested by the leave-one-out cross-validation. Four residents and two infectious disease specialists were tested using the summarized medical information. RESULTS: The training study comprised data from 60 patients with confirmed or probable TBM and 143 patients with confirmed VM. Older age, longer symptom duration before the visit, lower serum sodium, lower cerebrospinal fluid (CSF) glucose, higher CSF protein, and CSF adenosine deaminase were found in the TBM patients. Among the various machine-learning algorithms, the area under the curve (AUC) of the receiver operating characteristics of artificial neural network (ANN) with ImperativeImputer for matrix completion (0.85; 95% confidence interval 0.79 - 0.89) was found to be the highest. The AUC of the ANN model was statistically higher than those of all the residents (range 0.67 - 0.72, P <0.001) and an infectious disease specialist (AUC 0.76; P = 0.03). CONCLUSION: The machine-learning techniques may play a role in differentiating between TBM and VM. Specifically, the ANN model seems to have better diagnostic performance than the non-expert clinician.

Clinical Course and Molecular Viral Shedding Among Asymptomatic and Symptomatic Patients With SARS-CoV-2 Infection in a Community Treatment Center in the Republic of Korea.

IMPORTANCE: There is limited information about the clinical course and viral load in asymptomatic patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). OBJECTIVE: To quantitatively describe SARS-CoV-2 molecular viral shedding in asymptomatic and symptomatic patients. DESIGN, SETTING, AND PARTICIPANTS: A retrospective evaluation was conducted for a cohort of 303 symptomatic and asymptomatic patients with SARS-CoV-2 infection between March 6 and March 26, 2020. Participants were isolated in a community treatment center in Cheonan, Republic of Korea. MAIN OUTCOMES AND MEASURES: Epidemiologic, demographic, and laboratory data were collected and analyzed. Attending health care personnel carefully identified patients' symptoms during isolation. The decision to release an individual from isolation was based on the results of reverse transcription-polymerase chain reaction (RT-PCR) assay from upper respiratory tract specimens (nasopharynx and oropharynx swab) and lower respiratory tract specimens (sputum) for SARS-CoV-2. This testing was performed on days 8, 9, 15, and 16 of isolation. On days 10, 17, 18, and 19, RT-PCR assays from the upper or lower respiratory tract were performed at physician discretion. Cycle threshold (Ct) values in RT-PCR for SARS-CoV-2 detection were determined in both asymptomatic and symptomatic patients. RESULTS: Of the 303 patients with SARS-CoV-2 infection, the median (interquartile range) age was 25 (22-36) years, and 201 (66.3%) were women. Only 12 (3.9%) patients had comorbidities (10 had hypertension, 1 had cancer, and 1 had asthma). Among the 303 patients with SARS-CoV-2 infection, 193 (63.7%) were symptomatic at the time of isolation. Of the 110 (36.3%) asymptomatic patients, 21 (19.1%) developed symptoms during isolation. The median (interquartile range) interval of time from detection of SARS-CoV-2 to symptom onset in presymptomatic patients was 15 (13-20) days. The proportions of participants with a negative conversion at day 14 and day 21 from diagnosis were 33.7% and 75.2%, respectively, in asymptomatic patients and 29.6% and 69.9%, respectively, in symptomatic patients (including presymptomatic patients). The median (SE) time from diagnosis to the first negative conversion was 17 (1.07) days for asymptomatic patients and 19.5 (0.63) days for symptomatic (including presymptomatic) patients (P = .07). The Ct values for the envelope (env) gene from lower respiratory tract specimens showed that viral loads in asymptomatic patients from diagnosis to discharge tended to decrease more slowly in the time interaction trend than those in symptomatic (including presymptomatic) patients (ß = -0.065 [SE, 0.023]; P = .005). CONCLUSIONS AND RELEVANCE: In this cohort study of symptomatic and asymptomatic patients with SARS-CoV-2 infection who were isolated in a community treatment center in Cheonan, Republic of Korea, the Ct values in asymptomatic patients were similar to those in symptomatic patients. Isolation of asymptomatic patients may be necessary to control the spread of SARS-CoV-2.

Management and outcomes of Burkholderia cepacia complex bacteremia in patients without cystic fibrosis: a retrospective observational study.

Burkholderia cepacia complex (BCC) is an emerging pathogen of nosocomial infection in chronic or critically ill patients without cystic fibrosis (CF). The objective was to evaluate the management and outcomes of BCC bacteremia in patients without CF. We conducted a retrospective study of non-CF adult patients with BCC bacteremia between January 1997 and December 2016 at 4 tertiary hospitals in South Korea. A total of 216 non-CF patients with BCC bacteremia were identified. Most cases were hospital-acquired (79.2%), and the most common source was a central venous catheter (CVC) (42.1%). The rates of susceptibility to trimethoprim-sulfamethoxazole and piperacillin-tazobactam of BCC isolates were high as 92.8% and 90.3%, respectively. The rates of susceptibility to ceftazidime, meropenem, and levofloxacin were 75.5%, 72.3%, and 64.1%, respectively. The 14-day, 30-day, and in-hospital mortality rate was 19.4%, 23.1%, and 31.0%, respectively. Female (OR = 3.1; 95% CI, 1.4-6.8), liver cirrhosis (OR = 6.2; 95% CI, 1.6-16.6), septic shock (OR = 11.2; 95% CI, 5.1-24.8), and catheter-related infection (OR = 2.6, 95% CI, 1.2-5.8) were the independent risk factors for 30-day mortality. The outcome did not differ according to type of antibiotics used. Among 91 patients with CVC-related BCC bacteremia, delayed CVC removal (> 3 days) had a higher rate of persistent bacteremia (54.5 vs. 26.1%; P = 0.03) and lower rate of clinical response (49.0 vs. 71.9%; P = 0.04), compared with early CVC removal (within 3 days). BCC bacteremia occurring in non-CF patients was mostly hospital-acquired and CVC-related. Early removal of the catheter is crucial in treatment of CVC-related BCC bacteremia.

Etiology, characteristics, and outcomes of community-onset necrotizing fasciitis in Korea: A multicenter study.

BACKGROUND: Necrotizing fasciitis (NF) is a serious skin and soft tissue infection causing high mortality. Investigating region specific epidemiologic factors associated with NF is important for establishing appropriate treatment strategies. This multicenter study was done to provide an update of the microbial etiology, clinical characteristics, and outcomes of NF in Korea. MATERIALS AND METHODS: A retrospective cohort of adult patients with NF was established using patient data from 13 general hospitals between January 2012 and December 2015 in Korea. We evaluated microbial etiology and clinical characteristics to identify risk factors associated with in-hospital mortality; analyses were performed using binary logistic regression models. RESULTS: A total of 161 patients with NF were included. The most common underlying disease was diabetes mellitus (66 cases, 41.0%). A total of 148 organisms were isolated from 119 (73.9%) patients. Enteric Gram-negative organisms (36 patients) were the most common pathogen, followed by Staphylococcus aureus (30 patients) and streptococci (28 patients). Methicillin-resistant Staphylococcus aureus (MRSA) was identified in 6.2% (10/161) of patients. Of 37 enteric Gram-negative isolates tested, 26 (70.3%) isolates were susceptible to ceftriaxone. The in-hospital mortality rate was 22.4%. Intensive care unit admission, septic shock, and Gram-negative organism infections were significantly associated with in-hospital mortality, and surgery was not a favorable prognostic factor. CONCLUSIONS: As initial empirical antibiotics, glycopeptides against MRSA and broad-spectrum antibiotics against third-generation cephalosporin-resistant organisms should be considered for patients with community-onset NF in Korea.

Epidemiologic Trends and Clinical Features of Pneumocystis jirovecii Pneumonia in Non-HIV Patients in a Tertiary-Care Hospital in Korea over a 15-Year-Period.

Subsequent to the increasing use of immunosuppressant therapy, Pneumocystis jirovecii pneumonia (PcP) has emerged as a life-threatening condition in human immunodeficiency virus (HIV)-negative patients. We investigated changes in epidemiological and clinical characteristics among PcP cases with and without HIV infections. Data of 424 patients diagnosed with PcP in a 2,700-bed Korean tertiary care hospital between February 2003 and April 2017 were retrospectively analyzed. The study included patients with compatible clinical findings in whom PcP was confirmed via direct immunofluorescence assay. The annual average number of cases increased from 12.2 (initial 5-year period) to 42.2 (recent 5-year period). In HIV-negative patients, hematologic malignancy (34.8%) and solid organ transplantation (32.9%) were the most frequent major underlying conditions, and immunosuppressive therapies including corticosteroids (342/362, 94.5%) and chemotherapy (122/362, 33.7%) were significantly associated with PcP infection (p ＜ 0.001 for both). The incidence of PcP has continued to increase among non-HIV-infected immunocompromised patients in recent years.

Monomicrobial gram-negative necrotizing fasciitis: An uncommon but fatal syndrome.

This study aimed to characterize patients with monomicrobial gram-negative necrotizing fasciitis in three university hospitals in Korea. In this study, of the 115 patients with community-acquired necrotizing fasciitis, 67 (58%) had monomicrobial infections: 31 (27%) in the gram-negative group and 36 (31%) in the gram-positive group. The majority of patients in the gram-negative group were infected with Escherichia coli followed by Klebsiella pneumoniae and Vibrio vulnificus. More patients in the gram-negative group showed liver cirrhosis than those in the gram-positive group (39% vs. 14%, P = 0.02). In a multivariable logistic regression analysis, liver cirrhosis (adjusted odds ratio [aOR], 13.7; 95% confidence interval [CI], 2.9-67.0), treatment with antibiotics without surgery (aOR, 10.2; 95% CI, 2.1-48.3), and lower level of albumin (aOR 4.9; 95% CI, 1.6-14.9) were associated with 30-day mortality. Our findings suggest that gram-negative necrotizing fasciitis is more often associated with liver cirrhosis and has poorer outcomes than gram-positive necrotizing fasciitis.

Therapeutic outcome of spinal implant infections caused by Staphylococcus aureus: A retrospective observational study.

Spinal implant infection is a rare but significant complication of spinal fusion surgery, and the most common pathogen is Staphylococcus aureus. It is difficult to treat due to this pathogen's biofilm-forming ability and antibiotic resistance. We evaluated the therapeutic outcome of treatments for S aureus spinal implant infections. We retrospectively reviewed all patients with S aureus spinal implant infections at 11 tertiary-care hospitals over a 9-year period. Parameters predictive of treatment failure and recurrence were analyzed by Cox regression. Of the 102 patients with infections, 76 (75%) were caused by methicillin-resistant S aureus (MRSA) and 51 (50%) were late-onset infections. In all, 83 (81%) patients were managed by debridement, antibiotics, and implant retention (DAIR) and 19 (19%) had their implants removed. The median duration of all antibiotic therapies was 52 days. During a median follow-up period of 32 months, treatment failure occurred in 37 (36%) cases. The median time to treatment failure was 113 days, being <1 year in 30 (81%) patients. DAIR (adjusted hazard ratio [aHR], 6.27; P = .01) and MRSA infection (aHR, 4.07; P = .009) were independently associated with treatment failure. Rifampin-based combination treatments exhibited independent protective effects on recurrence (aHR, 0.23; P = .02). In conclusion, among patients with S aureus spinal implant infections, MRSA and DAIR were independent risk factors for treatment failure, and these risk factors were present in the majority of patients. In this difficult-to-treat population, the overall treatment failure rate was 36%; rifampin may improve the outcomes of patients with S aureus spinal implant infections.

Clinical Guidelines for the Antibiotic Treatment for Community-Acquired Skin and Soft Tissue Infection.

Skin and soft tissue infection (SSTI) is common and important infectious disease. This work represents an update to 2012 Korean guideline for SSTI. The present guideline was developed by the adaptation method. This clinical guideline provides recommendations for the diagnosis and management of SSTI, including impetigo/ecthyma, purulent skin and soft tissue infection, erysipelas and cellulitis, necrotizing fasciitis, pyomyositis, clostridial myonecrosis, and human/animal bite. This guideline targets community-acquired skin and soft tissue infection occurring among adult patients aged 16 years and older. Diabetic foot infection, surgery-related infection, and infections in immunocompromised patients were not included in this guideline.

Differences of cytomegalovirus diseases between kidney and hematopoietic stem cell transplant recipients during preemptive therapy.

BACKGROUND/AIMS: Cytomegalovirus (CMV) surveillance and preemptive therapy is a widely-used strategy for preventing CMV disease in transplant recipients. However, there are limited data on the incidence and patterns of CMV disease during the preemptive period. Thus, we investigated the incidence and pattern of tissue-invasive CMV disease in CMV seropositive kidney transplantation (KT) and hematopoietic stem cell transplantation (HCT) recipients during preemptive therapy. METHODS: We prospectively identified patients with tissue-invasive CMV disease among 664 KT (90%) and 496 HCT (96%) recipients who were D+/R+ (both donor and recipient seropositive) during a 4-year period. RESULTS: The incidence rates of CMV disease were 4.1/100 person-years (4%, 27/664) in KT recipients and 5.0/100 person-years (4%, 21/496) in HCT recipients. Twenty-six (96%) of the KT recipients with CMV disease had gastrointestinal CMV, whereas 17 (81%) of the HCT recipients had gastrointestinal CMV and 4 (19%) had CMV retinitis. Thus, CMV retinitis was more common among HCT recipients (p = 0.03). All 27 KT recipients with CMV disease suffered abrupt onset of CMV disease before or during preemptive therapy; 10 (48%) of the 21 HCT recipients with CMV disease were also classified in this way but the other 11 (52%) were classified as CMV disease following successful ganciclovir preemptive therapy (p < 0.001). CONCLUSIONS: The incidence of CMV disease was about 4% in both KT and HCT recipients during preemptive therapy. However, CMV retinitis and CMV disease as a relapsed infection were more frequently found among HCT recipients.

Clinical characteristics of hospital-onset Pneumocystis pneumonia and genotypes of Pneumocystis jirovecii in a single tertiary centre in Korea.

BACKGROUND: Pneumocystis pneumonia (PCP) may develop as a clinical manifestation of nosocomial pneumonia by means of either reactivation of resident P. jirovecii or de novo infection. However, there have been no studies describing the clinical characteristics of hospital-onset PCP. METHODS: A retrospective review of medical records was performed to identify episodes of hospital-onset PCP in a tertiary care centre in Korea between May 2007 and January 2013. We investigated whether human-to-human contact during hospitalisation contributed to PCP development by molecular analysis of the genes encoding mitochondrial large ribosomal subunit (mtLSU) rRNA and dihydropteroate synthase (DHPS) and a review of hospitalisation history. RESULTS: During the study period, 129 patients (130 episodes) were diagnosed with PCP. Of these, respiratory specimens from 94 patients during 95 PCP episodes were available for analysis. Sixteen episodes (16.8%) were categorised as hospital-onset PCP. There was a trend toward a higher proportion of haematological malignancy (43.8% [7/16] vs. 20.3% [16/79]; P = 0.058) in patients with hospital-onset PCP compared to patients with community-onset PCP. mtLSU genotype 1 was the most common, occurring in 41 (43.2%) patients. There were four possible cases of nosocomial transmission. Mutation in DHPS was not observed in any PCP episode. CONCLUSIONS: PCP can be one of the causes of nosocomial pneumonia, although the mode of acquisition and transmission of P. jirovecii remains uncertain. mtLSU genotype 1 is the predominant P. jirovecii strain in Korea.

Point prevalence of Pneumocystis pneumonia in patients with non-Hodgkin lymphoma according to the number of cycles of R-CHOP chemotherapy.

R-CHOP chemotherapy composed of rituximab, cyclophosphamide, adriamycin, vincristine, and prednisolone which might increase the risk of Pneumocystis pneumonia in patients with non-Hodgkin lymphoma. We estimated the point prevalence of Pneumocystis pneumonia in non-Hodgkin lymphoma patients according to the number of R-CHOP cycles and investigated whether cytoreduction by chemotherapy is associated with Pneumocystis pneumonia development. We retrospectively established a cohort of patients who received R-CHOP for non-Hodgkin lymphoma in our institution. Using this cohort, we estimated the incidence rate and point prevalence of definite and probable Pneumocystis pneumonia. To assess factors associated with Pneumocystis pneumonia development several clinical variables, including absolute neutrophil and lymphocyte count at the time of non-Hodgkin lymphoma diagnosis and when the last R-CHOP cycle was administered, were compared between patients with and without Pneumocystis pneumonia. Of 713 patients in the cohort, 14 and 18 patients were diagnosed with definite and probable Pneumocystis pneumonia, respectively. The overall incidence of definite and definite plus probable PCP in NHL patients receiving R-CHOP were 2.0 % (14/713; 95 % CI, 1.1-3.3 %) and 4.5 % (32/713; 95 % CI, 3.2-6.4 %), respectively. This corresponded to 3.8 (95 % CI, 2.2-6.4) and 8.4 (95 % CI, 5.9-11.9) per 1000 persons. Many cases of Pneumocystis pneumonia (22/32, 68.7 %) developed after administration of the fourth R-CHOP cycle. However, there was no statistical difference in Pneumocystis pneumonia prevalence between patients receiving four or more cycles of R-CHOP and fewer than. Higher absolute neutrophil count (4,742/mm(3) vs. 2,627/mm(3); p < 0.01) was associated with Pneumocystis pneumonia development at the last R-CHOP cycle, while absolute lymphocyte count at the time of NHL diagnosis was not. Contrary to expectations, Pneumocystis pneumonia is not a frequent complication of R-CHOP treatment for non-Hodgkin lymphoma. Cytoreduction of R-CHOP might not be a risk factor of Pneumocystis pneumonia development. Universal prophylaxis against Pneumocystis pneumonia during R-CHOP treatment could not be strongly recommended.

Risk factors for mortality in patients with invasive mucormycosis.

BACKGROUND: Mucormycosis is an uncommon and life-threatening fungal infection. The clinical predictors of outcome were evaluated in patients with invasive mucormycosis. MATERIALS AND METHODS: We retrospectively reviewed histologically proven cases of invasive mucormycosis in our institution from 1996 to 2012. RESULTS: A total of 64 patients were analyzed. The median age was 59 years (interquartile range [IQR], 50-67), and 32 patients (50%) were male. The most common underlying diseases were diabetes mellitus (67%), hematologic malignancy (22%), and solid cancer (19%). The most common infection sites were the rhino-orbito-cerebral area (56%) and the lungs (31%). The 180-day all-cause mortality was 33%. Disseminated infection was associated with increased mortality (hazard ratio [HR]: 169.74, 95% confidence interval [CI]: 6.41 to 4492.64; P = 0.002). Pulmonary infection (HR: 0.08, 95% CI: 0.01 to 0.66; P = 0.02) and complete surgical removal of infected tissue (HR: 0.12, 95% CI: 0.02 to 0.64; P = 0.01) were associated with decreased mortality. CONCLUSIONS: These results suggest that patients with mucormycosis had a lower risk of mortality if they developed a pulmonary infection, rather than a disseminated infection and with complete debridement of infected tissue.

Outcomes of non-HIV-infected patients with Pneumocystis pneumonia and concomitant pulmonary cytomegalovirus infection.

BACKGROUND: The pathogenic effect of concomitant pulmonary cytomegalovirus (CMV) infection on morbidity and mortality of Pneumocystis jirovecii pneumonia (PCP) has been questioned in the case of non-HIV-infected patients. METHODS: We conducted a retrospective cross-sectional study of patients who were diagnosed with PCP by bronchoalveolar lavage. We compared demographics, clinical characteristics, morbidity, and mortality in non-HIV-infected PCP patients with (n = 31) and without (n = 75) pulmonary CMV infection. Morbidity was assessed by length of hospital stay, admission to the intensive care unit, and use of mechanical ventilation. Mortality was defined as 30-day and 90-day all-cause mortality. RESULTS: Morbidity and mortality did not differ between PCP patients with and without pulmonary CMV infection. In multivariate analysis using the Cox proportional hazard model, haematological malignancy (relative risk (RR) 0.20, 95% confidence interval (95% CI) 0.06-0.71), PCP treatment duration (RR 0.81, 95% CI 0.75-0.88), changing to a second-line regimen due to treatment failure (RR 4.51, 95% CI 1.61-12.64), and mechanical ventilation (RR 17.99, 95% CI 4.83-67.04) were independently associated with 30-day all-cause mortality. Being a solid organ transplant recipient (RR 0.17, 95% CI 0.05-0.56) and the use of mechanical ventilation (RR 6.49, 95% CI 2.84-14.83) were independently associated with 90-day all-cause mortality. However, concomitant pulmonary CMV infection was not associated with either 30-day or 90-day mortality. CONCLUSIONS: Our results suggest that concomitant pulmonary CMV infection does not significantly affect the prognosis of PCP, as indicated by morbidity and mortality in non-HIV-infected patients with PCP. Based on this result, we propose that it is not essential to administer an anti-CMV regimen when CMV is co-isolated from the bronchoalveolar lavage in patients with PCP.

Outcomes of moderate-to-severe Pneumocystis pneumonia treated with adjunctive steroid in non-HIV-infected patients.

While it is well-known that adjunctive corticosteroid use improves the outcome of moderate-to-severe Pneumocystis jirovecii pneumonia (PcP) in patients with human immunodeficiency virus (HIV), there are limited data on its efficacy in non-HIV-infected patients with PcP. Patients undergoing fiber-optic bronchoscopy with bronchoalveolar lavage for suspected PcP from January 2007 through December 2010 were reviewed retrospectively. We compared demographics, clinical characteristics, and outcomes in 88 non-HIV-infected patients with moderate-to-severe PcP with (n = 59) and without (n = 29) adjunctive corticosteroid use. Outcomes of PcP were assessed by respiratory failure and 30-day and 90-day all-cause mortality. Survival curves were analyzed by the Kaplan-Meier method and estimated by the log rank test. All-cause mortality of moderate-to-severe PcP at 90 days was lower in the solid-organ transplant recipients than in all other patients (6/26 [23%] versus 34/62 [55%], respectively; P = 0.006), and mortality at 30 days was lower in patients with hematologic malignancies than in all other patients (4/26 [15%] versus 24/62 [39%], respectively; P = 0.03). The outcomes of PcP were not significantly different in moderate-to-severe PcP patients with and without adjunctive corticosteroid use, regardless of recent corticosteroid use. Survival analysis of PcP patients with and without corticosteroid use by the Kaplan-Meier method also did not reveal any difference (log rank test; P = 0.81). There again was no difference within the subgroup of PcP patients with solid-organ transplants. Adjunctive corticosteroid use may not improve the outcome of moderate-to-severe PcP in non-HIV-infected patients.

A case of histiocytic sarcoma presenting with primary bone marrow involvement.

Histiocytic sarcoma (HS) is a very rare neoplasm that often shows an aggressive clinical course and systemic symptoms, such as fever, weight loss, adenopathy, hepatosplenomegaly and pancytopenia. It may present as localized or disseminated disease. We describe here a 63-yr-old male who manifested systemic symptoms, including fever, weight loss and generalized weakness. Abdominal and chest computed tomography failed to show specific findings, but there was suspicion of multiple bony changes at the lumbar spine. Fusion whole body positron emission tomography, bone scan and lumbar spine magnetic resonance imaging showed multiple bone lesions, suggesting a malignancy involving the bone marrow (BM). Several BM and bone biopsies were inconclusive for diagnosis. Necropsy showed replacement of the BM by a diffuse proliferation of neoplastic cells with markedly increased cellularity (95%). The neoplastic cells were positive for lysozyme and CD68, but negative for T- and B-cell lineage markers, and megakaryocytic, epithelial, muscular and melanocytic markers. Morphologic findings also distinguished it from other dendritic cell neoplasms.