A 71-Year-Old Man With Diffuse Waxing and Waning Multifocal Lung Lesions, Empyema, and Episodic Fevers Reveals a Rare Diagnosis.

CASE PRESENTATION: A 71-year-old man with history of gastroesophageal reflux disease, chronic sinusitis, arthritis, hypothyroidism, and anemia of chronic disease initially sought treatment with a recurrent left pleural effusion along with other abnormal lung findings on chest CT scan. Before his referral, he was being managed for 3 years at his local hospital for waxing and waning fevers, fatigue, productive cough, chills, and night sweats. He did not report any hemoptysis or chest pain, but reported weight loss of 13 kgs in 15 months. During those 3 years, he was treated with multiple courses of antibiotics and steroids with temporary relief of symptoms. At that time, his chronic sinusitis was suspected to be the cause of his symptoms and he underwent balloon sinuplasty. He was receiving daily sublingual immunotherapy for inhaled respiratory allergens for the previous year after showing positive test results for 17 inhaled allergens. The patient had no other known immunologic workup before our evaluation.

Meta-analysis investigating the relationship between clinical features, outcomes, and severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia.

OBJECTIVE: We aimed to investigate the relationship between clinical characteristics, outcomes and the severity of severe acute respiratory syndrome coronavirus 2 pneumonia. METHODS: We performed a systematic review and meta-analysis using PubMed, Embase, and Cochrane Library databases to assess the clinical characteristics and outcomes of confirmed COVID-19 cases and compared severe (ICU) and nonsevere (non-ICU) groups. RESULTS: We included 12 cohort studies including 2,445 patients with COVID-19. Compared with nonsevere (non-ICU) patients, severe (ICU) disease was associated with a smoking history (P = .003) and comorbidities including chronic obstructive pulmonary disease (OR = 5.08, P < .001), diabetes (OR = 3.17, P < .001), hypertension (OR = 2.40, P < .001), coronary heart disease (OR = 2.66, P < .001), cerebrovascular diseases (OR = 2.68, P = .008), and malignancy (OR=2.21, P = .040). We found significant differences between the 2 groups for fever, dyspnea, decreased lymphocyte and platelet counts, and increased leukocyte count, C-creative protein, procalcitonin, lactose dehydrogenase, aspartate aminotransferase, alanine aminotransferase, creatinine kinase, and creatinine levels (P < .05). Significant differences were also observed for multiple treatments (P < .05). Patients in the severe (ICU) group were more likely to have complications and had a much higher mortality rate and lower discharge rate than those with nonsevere (non-ICU) disease (P < .05). CONCLUSIONS: Investigation of clinical characteristics and outcomes of severe cases of COVID-19 will contribute to early prediction, accurate diagnosis, and treatment to improve the prognosis of patients with severe illness.

Case Report: Anaplasmosis in Canada: Locally Acquired Anaplasma phagocytophilum Infection in Alberta.

Human granulocytic anaplasmosis is an obligate intra-granulocytic parasite that is transmitted by Ixodes scapularis and Ixodes pacificus in North America. We report on the second laboratory-confirmed case of Anaplasma phagocytophilum acquired within the province of Alberta, Canada. A 67-year-old woman from the Edmonton health zone developed nonspecific systemic symptoms including fatigue, night sweats, myalgia, headaches, and fever 6 days after noticing a tick on her left upper arm in May of 2017 (day 0). On day 13, she was found to have thrombocytopenia. Her symptoms progressed until day 16 when she was treated empirically with doxycycline, at which time she slowly improved over the subsequent 2 months. The tick was later identified as a partially engorged female blacklegged tick, I. scapularis, and it was positive for A. phagocytophilum DNA by PCR. Anaplasma serology performed retrospectively on blood samples collected on days 13, 31, and 52 showed a greater than 4-fold increase in A. phagocytophilum (IgG titers from less than 1:64 on day 13 to 1:2048 on days 31 and 52), consistent with an acute infection. Although populations of blacklegged ticks are not yet established in Alberta, suspicion should remain for tick-borne diseases because infected ticks are introduced into the province by migrating birds. This case report highlights the need to remind physicians and other public health professionals that rare, non-endemic tick-borne diseases can occasionally occur in low-risk jurisdictions.

Persistent leukocytosis in polycythemia vera is associated with disease evolution but not thrombosis.

There are unresolved questions regarding the association between persistent leukocytosis and risk of thrombosis and disease evolution in polycythemia vera (PV), as much of the published literature on the topic does not appropriately use repeated-measures data or time-dependent modeling to answer these questions. To address this knowledge gap, we analyzed a retrospective database of 520 PV patients seen at 10 academic institutions across the United States. Taking hematologic laboratory data at ∼3-month intervals (or as available) for all patients for duration of follow-up, we used group-based trajectory modeling to identify latent clusters of patients who follow distinct trajectories with regard to their leukocyte, hematocrit, and platelet counts over time. We then tested the association between trajectory membership and hazard of 2 major outcomes: thrombosis and disease evolution to myelofibrosis, myelodysplastic syndrome, or acute myeloid leukemia. Controlling for relevant covariates, we found that persistently elevated leukocyte trajectories were not associated with the hazard of a thrombotic event (P = .4163), but were significantly associated with increased hazard of disease evolution in an ascending stepwise manner (overall P = .0002). In addition, we found that neither hematocrit nor platelet count was significantly associated with the hazard of thrombosis or disease evolution.

Pre-chemotherapy white blood cell depletion by therapeutic leukocytapheresis in leukemia patients: A single-institution experience.

BACKGROUND: Hyperleukocytosis is commonly seen in acute and chronic leukemias. Therapeutic leukocytapheresis using an automatic cell separator can help to achieve prompt leukoreduction to reduce the rate of thrombotic events and early mortality as well as to prevent tumor lysis syndrome. AIM: In this study, we report a single center's experience in managing leukemia patients with therapeutic leukocytapheresis prior to chemotherapy. MATERIALS AND METHODS: Leukocytapheresis procedures were performed in 192 leukemia patients (including acute myeloid leukemia [AML], acute lymphoblastic leukemia [ALL], and chronic myeloid leukemia [CML]) with hyperleukocytosis between January and December 2016. RESULTS: Median % reduction of white blood cell (WBC) count was 30.5% and median % removal efficiency was 46.7% for 75 procedures where the waste bag was sampled. WBC removal efficiency strongly depended on diagnosis (and was 71%, 66%, and 39% for ALL, AML, and CML, respectively). Procedures were generally well tolerated with only 9 out of 192 patients having mild adverse effects. DISCUSSION AND CONCLUSION: In the absence of specific guidelines for the management of hyperleukocytosis, leukocytapheresis in association with chemotherapy should be considered early in clinical practice.

Clinical and biochemical differences between hantavirus infection and leptospirosis: a retrospective analysis of a patient series in Belgium.

Objectives: Hantavirus infection and leptospirosis are infectious diseases transmitted by rodents. The clinical picture is nonspecific, often involving the kidneys but other organs can be affected too. Clinical and biochemical clues to make a difference between these two entities will be described.Methods: A retrospective analysis was performed on a database of patients presenting between January 2012 and September 2017 at the emergency department of the university hospital Leuven, Belgium. Patients were selected on the basis of a compatible clinical picture, biochemistry, and microbiological evidence. Presenting complaints and clinical examination were compared. Blood, taken at presentation, was used for hematological and biochemical analysis.Results: Sixteen patients with hantavirus infection and eight patients with leptospirosis were identified. All patients complained about general malaise and fever. Other frequent complaints were myalgia and a headache. Patients with leptospirosis often experienced photo- or sonophobia.Looking for neck stiffness and eye lesions might help to diagnose leptospirosis.Differences in biochemistry between viral and bacterial disease could be recognized; high C-reactive protein (CRP) and leukocytosis with left shift favor leptospirosis, elevated lactate dehydrogenase (LDH) favors viral infection. Abnormal liver function with raised total bilirubin is often seen in cases with leptospirosis.Conclusion: This study demonstrates some subtle clues that may help to differentiate between hantavirus infection and leptospirosis in patients presenting to a hospital in a nonendemic region of the world. Because of small number of patients, we could not identify significant clinical or biochemical tests. Serology remains the gold standard.

Exercise reduces inflammatory cell production and cardiovascular inflammation via instruction of hematopoietic progenitor cells.

A sedentary lifestyle, chronic inflammation and leukocytosis increase atherosclerosis; however, it remains unclear whether regular physical activity influences leukocyte production. Here we show that voluntary running decreases hematopoietic activity in mice. Exercise protects mice and humans with atherosclerosis from chronic leukocytosis but does not compromise emergency hematopoiesis in mice. Mechanistically, exercise diminishes leptin production in adipose tissue, augmenting quiescence-promoting hematopoietic niche factors in leptin-receptor-positive stromal bone marrow cells. Induced deletion of the leptin receptor in Prrx1-creERT2; Leprfl/fl mice reveals that leptin's effect on bone marrow niche cells regulates hematopoietic stem and progenitor cell (HSPC) proliferation and leukocyte production, as well as cardiovascular inflammation and outcomes. Whereas running wheel withdrawal quickly reverses leptin levels, the impact of exercise on leukocyte production and on the HSPC epigenome and transcriptome persists for several weeks. Together, these data show that physical activity alters HSPCs via modulation of their niche, reducing hematopoietic output of inflammatory leukocytes.

Hyperleukocytosis increases risk of fatal hyperkalemia with new ibrutinib/venetoclax regimen for refractory mantle cell lymphoma.

Background: A recent phase 2 study reported success using combination of ibrutinib and venetoclax for relapsed/refractory mantle cell lymphoma (MCL). We report a case of MCL with hyperleukocytosis that developed fatal hyperkalemia after a single low initiation dose of venetoclax.Case report: A 72-year-old man with known MCL was admitted for hyperkalemia and anemia (Hgb = 6.6 g/dL, K+ =9.6 mmol/L). Repeated K+ measurements and clinical evaluation were consistent with pseudohyperkalemia. The patient's lymphocyte count had risen from 15.2 to 466.8 K/uL in the preceding 1.5 months despite 8 cycles of ibrutinib. Based on the results of a recent phase 2 study Venetoclax was added; after a single very low initiation dose of venetoclax the patient developed fatal hyperkalemia.Discussion: The proliferation of new therapies is making difficult to perform randomized clinical trials large enough to capture potential risks of new therapies in specific scenarios. Fatal hyperkalemia resulted from use of a recently recommended combination regimen for refractory/relapsed MCL in a phase 2 study, despite dose escalation and TLS prophylaxis suggesting increased risk of this regimen for patients with hyperleukocytosis.

Leukocytosis and neutrophilia after laparoscopic gastric plication.

BACKGROUND: Laparoscopic gastric plication (LGP) is a relatively novel bariatric surgery technique. We have encountered a noticeable proportion of our LGP patients with findings such as leukocytosis and neutrophilia and hypothesized that they are part of normal body response to the operation. OBJECTIVE: To evaluate the prevalence and clinical importance of leukocytosis, neutrophilia and abnormal vital signs in patients undergoing LGP during postoperative period. METHODS: Forty-four consecutive LGP patients were prospectively followed for 3 months. Records of 44 laparoscopic cholecystectomy patients were also reviewed for comparison. Preoperative and postoperative laboratory test were performed. Minor and major complications were recorded during the study period. RESULTS: Mean body mass index (BMI) and age were 37and 42.5, respectively. Mean hospital stay was 3.6 days (range: 3-8 days). Leukocytosis and neutrophilia were detected in 63% and 72% of the LGP patients, respectively, 48 h after the procedure. Whereas, after cholecystectomy only 38.5% and 18% of patients had leukocytosis and neutrophilia, respectively. 25% of the patients suffered from at least one minor complication after LGP. There was no mortality. CONCLUSIONS: Leukocytosis and neutrophilia are very common after LGP in both the complicated and uncomplicated cases, and may be a part of normal response to surgery.

Elevated serum levels of free interleukin-18 in adult-onset Still's disease.

OBJECTIVE: IL-18 is a pro-inflammatory cytokine of the IL-1 family that is naturally inhibited by IL-18 binding protein (IL-18BP). High levels of IL-18 have been described in the serum of adult-onset Still's disease (AOSD) patients, but only total IL-18 levels (including inactive IL-18 bound to IL-18BP) have been measured. With a specific immunoassay, we aimed to measure free IL-18 serum levels in AOSD patients and other rheumatic diseases. METHODS: An ELISA was developed to measure free IL-18. Its sensitivity and specificity were tested by spiking recombinant IL-18 or IL-18BP in serum and PBS supplemented with 5% BSA. The binding affinity of IL-18 to IL-18BP was calculated by titration experiments using the ELISA and by Biacore analysis. Sera of 37 AOSD patients and 138 controls (40 healthy controls, 30 RA, 29 SLE, 21 AS and 18 PsA) were assayed for free IL-18, IL-18BP, total IL-18 and other cytokines. Correlations were performed between free IL-18 and markers of disease activity in AOSD patients. RESULTS: Free IL-18 serum levels were significantly higher in AOSD patients (median 8.89 pg/ml) than in healthy and disease controls (1.37 pg/ml; P < 0.01). Free IL-18 serum levels correlated with AOSD activity. The affinity of IL-18 to IL-18BP was found to be much higher than previously described, with a dissociation constant ranging from 30 to 50 pM. CONCLUSION: Free IL-18 levels are specifically elevated in AOSD compared with other inflammatory diseases, suggesting that IL-18 represents a potential target for the treatment of AOSD.

Síndrome HaNDL: correlación entre la topografía del déficit neurológico y las alteraciones en electroencefalograma y SPECT en una serie de 5 nuevos casos / HaNDL syndrome: Correlation between focal deficits topography and EEG or SPECT abnormalities in a series of 5 new cases

Introducción: El síndrome de cefalea transitoria y déficits neurológicos con linfocitosis de líquido cefalorraquídeo (LCR), conocido por su acrónimo en inglés, HaNDL, se caracteriza por episodios de cefalea de características migrañosas acompañados por síntomas deficitarios motores, sensitivos o de lenguaje. El electroencefalograma (EEG) o la tomografía por emisión de fotón único (SPECT) pueden mostrar anomalías focales consistentes con los déficits neurológicos. Pretendemos evaluar dicha correlación en una serie de 5 nuevos pacientes. Pacientes: Análisis retrospectivo de pacientes atendidos en un hospital terciario (enero del 2010-mayo del 2014, 5 casos [3 varones, 2 mujeres]), de 30,6 ± 7,7 años (21-39). Presentaron 3,4 ± 2,6 (2-8) episodios de cefalea moderada-severa y déficits neurológicos durante un tiempo no superior a 5 semanas. En todos, pleocitosis de LCR (70 a 312 células/mm3, 96,5-100% linfocitos), con estudio etiológico negativo. Resultados: EEG en 4 pacientes y SPECT en 3. Caso 1: 8 episodios, 4 de hemisferio izquierdo, 3 hemisferio derecho y 1 de tronco, 2 EEG con enlentecimiento temporal izquierdo y bitemporal; SPECT normal. Caso 2: 2 cuadros, hemisférico izquierdo y hemisférico derecho respectivamente y SPECT con flujo disminuido temporal izquierdo. Caso 3: 3 episodios hemisféricos izquierdos; EEG con enlentecimiento temporo-frontal bilateral. Caso 4: 2 cuadros con topografía parieto-occipital derecha y EEG con enlentecimiento frontal derecho. Caso 5: 2 episodios, hemisférico derecho y hemisférico izquierdo, EEG con enlentecimiento temporal derecho; SPECT normal. Conclusiones: Existe gran heterogeneidad clínica en los déficits neurológicos del HaNDL; las alteraciones en SPECT y, sobre todo, en EEG no son infrecuentes y no siempre se relacionan con la topografía clínica

Introduction: Transient headache and neurological deficits with cerebrospinal fluid lymphocytosis (HaNDL) is characterised by migraine-like headache episodes accompanied by neurological deficits consisting of motor, sensory, or aphasic symptoms. Electroencephalogram (EEG) and single photon emission computed tomography (SPECT) may show focal abnormalities that correspond to the neurological deficits. We aim to evaluate the correlation between focal deficit topography and EEG or SPECT abnormalities in 5 new cases. Patients: We retrospectively reviewed patients attended in a tertiary hospital (January 2010-May 2014) and identified 5 patients (3 men, 2 women) with a mean age of 30.6 ± 7.7 (21-39) years. They presented 3.4 ± 2.6 episodes of headache (range, 2-8) of moderate to severe intensity and transient neurological deficits over a maximum of 5 weeks. Pleocytosis was detected in CSF in all cases (70 to 312 cells/mm3, 96.5-100% lymphocytes) with negative results from aetiological studies. Results: At least one EEG was performed in 4 patients and SPECT in 3 patients. Patient 1: 8 episodes; 4 left hemisphere, 3 right hemisphere, and 1 brainstem; 2 EEGs showing left temporal and bilateral temporal slowing; normal SPECT. Patient 2: 2 episodes, left hemisphere and right hemisphere; SPECT showed decreased left temporal blood flow. Patient 3: 3 left hemisphere deficits; EEG with bilateral frontal and temporal slowing. Patient 4: 2 episodes with right parieto-occipital topography and right frontal slowing in EEG. Patient 5: 2 episodes, right hemisphere and left hemisphere, EEG with right temporal slowing; normal SPECT. Conclusion: The neurological deficits accompanying headache in HaNDL demonstrate marked clinical heterogeneity. SPECT abnormalities and most of all EEG abnormalities were not uncommon in our series and they did not always correlate to the topography of focal deficits

Disordered haematopoiesis and athero-thrombosis.

Atherosclerosis, the major underlying cause of cardiovascular disease, is characterized by a lipid-driven infiltration of inflammatory cells in large and medium arteries. Increased production and activation of monocytes, neutrophils, and platelets, driven by hypercholesterolaemia and defective high-density lipoproteins-mediated cholesterol efflux, tissue necrosis and cytokine production after myocardial infarction, or metabolic abnormalities associated with diabetes, contribute to atherogenesis and athero-thrombosis. This suggests that in addition to traditional approaches of low-density lipoproteins lowering and anti-platelet drugs, therapies directed at abnormal haematopoiesis, including anti-inflammatory agents, drugs that suppress myelopoiesis, and excessive platelet production, rHDL infusions and anti-obesity and anti-diabetic agents, may help to prevent athero-thrombosis.

Therapeutic leukocytapheresis for improvement in respiratory function in a woman with hyperleukocytosis and mantle cell lymphoma with a circulating small lymphocyte phenotype.

Mantle cell lymphoma is an aggressive malignant B-cell disorder that often presents with a leukemic picture. Circulating lymphoma cell morphology may vary from small round mature-appearing lymphocytes resembling the lymphocytes of chronic lymphocytic leukemia to large prolymphocytoid or blastoid cells. Rare reports of hyperleukocytosis with leukostasis, treated with leukocytapheresis, are described in patients with prolymphocytoid or blastoid morphology. We report an 88 year old woman with mantle cell lymphoma, hyperleukocytosis (WBC > 400 × 10(3) /µL) with severe respiratory compromise but without interstitial or alveolar infiltrates on radiograph or computerized tomography of the chest. She was afebrile and had no central nervous system signs. Circulating lymphoma cell morphology was predominantly of the small lymphocyte type. A two-whole-blood-volume leukocytapheresis reduced her WBC from 465 to 221 × 10(3) /µL in 150 min. Her respiratory rate decreased from 28/min to 18/min and her arterial oxygen saturation (SpO2 ) rose from 91% to 97% on 6 L/min of oxygen by nasal cannula. Severe breathlessness before the procedure abated completely by the end of the procedure. Respiratory compromise may occur in mantle cell lymphoma with hyperleukocytosis with a mature lymphoma cell phenotype, even without a clear picture of leukostasis. Although the ultimate survival of the patient depends on treatment with chemotherapy, leukocytapheresis for alleviation of symptoms may be warranted and should be considered. Respiratory status and response to leukocytapheresis should be documented with physiological measurements. J. Clin. Apheresis 31:398-402, 2016. © 2015 Wiley Periodicals, Inc.

Genetic and baseline metabolic factors for incident diabetes and HbA(1c) at follow-up: the healthy twin study.

BACKGROUND: We investigated baseline anthropometric/metabolic traits predicting incident diabetes, genetic/environmental relationships between these traits and HbA1c at follow-up and the contribution of genetics, covariates and environments to variance in HbA(1c) at follow-up and incident diabetes. METHODS: Nondiabetic twins (n = 869) and their family members (n = 949) were followed over 3.7 ± 1.4 years (44.3 ± 12.8 years of age); baseline anthropometric/metabolic traits were measured. Fasting plasma glucose and HbA(1c) were measured at follow-up. Incident diabetes was defined as HbA(1c) ≥6.5% or fasting plasma glucose ≥7 mmol/L. RESULTS: Age-adjusted incident diabetes was 4.9% in men and 4.1% in women. Odd ratio for incident diabetes was 2.34-2.40, 1.25-1.28, 1.22-1.27 and 1.89 per standard deviation of baseline fasting plasma glucose, white blood cell (WBC), triglycerides and waist circumference, respectively, in multivariate generalized estimating equation models (p < 0.05). Age-adjusted and sex-adjusted heritability was 0.85 for diabetes and 0.72 for HbA(1c). In bivariate analyses adjusted for age, sex and body mass index at baseline, HbA1c at follow-up showed significant genetic and environmental correlations with baseline glucose (0.44, 0.17), significant genetic correlation with baseline waist circumference (0.16) and triglycerides (0.30) and significant environmental correlation with baseline WBC (0.09). Variance in HbA1c at follow-up and incident diabetes was explained by genetics (33% and 28%, respectively), covariates (36% and 48%, respectively), shared environments (7% and 0%, respectively) and errors (24% and 24%, respectively). CONCLUSIONS: High values for baseline fasting plasma glucose, WBC, triglycerides and waist circumference are independent risk factors for incident diabetes. While genetic influences strongly contribute to variance in HbA1c at follow-up and incident diabetes, these risk factors significantly contribute to the remaining variance.

Comparison of gestational diabetes mellitus rates in women with increased and normal white blood cell counts in early pregnancy.

AIM: To compare the rates of gestational diabetes mellitus (GDM) among Thai or other South-East Asian women with increased and normal peripheral white blood cell (WBC) counts in early pregnancy. The risk of GDM in relation to WBC count was also determined. METHODS: We included singleton pregnant women who sought their first antenatal care in our institution between May 2010 and December 2011. Subjects were 595 gravidas with an increased WBC count while controls were 595 pregnancies with a normal WBC count. Data of pregnant women were collected. The WBC of each woman was obtained from a complete blood count performed in the first trimester. The rates of GDM between both groups were compared. The odds ratio (OR) with 95% confidence interval (CI) of GDM development in the subject group was determined by multivariate analysis. RESULTS: Data on 570 subjects with increased WBC and 575 controls with normal WBC were obtained. The rate of GDM was significantly higher in subjects compared to controls at 13.2% versus 5.2% (P<0.001) with a crude OR of 2.75 (95% CI, 1.77-4.28). By multivariate analysis, the subject group was found at increased risk of GDM compared to the control group, with an adjusted OR of 2.20 (95% CI, 1.39-3.47). CONCLUSION: Thai or other South-East Asian women with an increased WBC count in early pregnancy had a significantly higher rate of GDM than women having a normal WBC count. Our results demonstrate that WBC count is an independent risk factor for GDM.

Interaction between leukocytes and erythrocytes in the human retina: effects of pentoxifylline on hyperoxia-induced vasoconstriction during increased neutrophil counts.

PURPOSE: Pentoxifylline, a nonselective phosphodiesterase inhibitor, shows vasodilator effects in certain vascular beds and reduces blood viscosity. We have previously shown that under states of vasoconstriction an interaction between circulating erythrocytes and leukocytes may play a role in the control of blood flow. The reason for this observation is not entirely clear but may be related to a mechanical interaction between red and white blood cells. In the present study we hypothesized that pentoxifylline may alter this interaction during oxygen-induced vasoconstriction. METHODS: 24 healthy male subjects participated in this double masked, randomized, placebo-controlled 2 way cross over trial. In order to increase white blood cell count (WBC) count, 300 µg of G-CSF was administered intravenously. Vasoconstriction of retinal vessels was induced by oxygen inhalation. 400mg of pentoxifylline or placebo was infused at two different study days. White blood cell flux was assessed with the blue-field entoptic technique. Vessel calibers were measured with a dynamic vessel analyzer (DVA) and red blood cell velocity (RBCV) was determined with laser Doppler velocimetry (LDV). Retinal blood flow was calculated based on retinal vessel diameters and RBCV. RESULTS: Administration of G-CSF induced a significant increase in WBC, both in the placebo and the pentoxifylline group (p<0.01 for both groups). Retinal vessel diameter, RBCV, calculated retinal blood flow and white blood cell flow were not altered by administration of pentoxifylline. Hyperoxia induced a pronounced decrease in retinal blood flow parameters. No difference was observed between groups during oxygen breathing in vessel diameters (p=0.54), RBCV (p=0.34), calculated retinal blood flow (p=0.3) and white blood cell flow (p=0.26). CONCLUSION: Our data indicate that short time administration of pentoxifylline does not alter the oxygen-induced effect on ocular blood flow parameters during leukocytosis. Whether long-term treatment could improve retinal blood flow under states of vasoconstriction remains to be investigated.