Osteoarthritis year in review 2020: rehabilitation and outcomes.

OBJECTIVE: Systematically review and synthesize guidelines, systematic reviews, or randomized controlled trials (RCTs) published between April 1, 2019 and April 30, 2020 which evaluated or made recommendations for rehabilitation of persons with osteoarthritis. DESIGN: Five electronic databases (Medline, EMBASE, Cochrane CENTRAL, CINHAL, Web of Science) were searched with a comprehensive search strategy. Guidelines for rehabilitation of persons with osteoarthritis, and systematic reviews and RCTs evaluating osteoarthritis rehabilitation that included at least one patient-reported outcome measure and/or clinical test of function were included. Two authors independently screened records and assessed methodological quality using the AGREE-II (guidelines), AMSTAR-2 (systematic reviews) or PEDro scale (RCTs). Data were extracted to summarize included records and a narrative synthesis of findings related to core recommended osteoarthritis rehabilitation treatments performed. RESULTS: Of 2,479 potential records, 253 records were reviewed. Two guidelines, 18 systematic reviews and 38 RCTs were included. 84% (n = 49) of included records related to knee osteoarthritis, 13% (n = 8) to hip, 10% (n = 6) to hand, 3% (n = 2) to mixed, and 1% (n = 1) to foot osteoarthritis. Exercise-therapy, methods to deliver exercise-therapy remotely, and approaches to facilitate exercise-therapy behaviour change were the most commonly evaluated interventions (n = 27). 94% of systematic reviews and 63% of RCTs rated high-quality. CONCLUSIONS: Osteoarthritis rehabilitation research continues to focus on knee osteoarthritis and exercise-based interventions. Emerging topics include rehabilitation of comorbid populations, exercise behaviour change and technology supports. A better understanding of rehabilitation of osteoarthritis in joints other than the knee, and methods to determine and promote ideal exercise-therapy prescription are needed.

Long isoform of ErbB3 binding protein, p48, mediates protein kinase B/Akt-dependent HDM2 stabilization and nuclear localization.

p48 is a long isoform of the ErbB3 binding protein that has oncogenic functions including promotion of carcinogenesis and induction of malignant transformation through negative regulation of tumor suppressor p53. Here, we show that high level of p48 protein expression leads to enhance HDM2 phosphorylation by Akt and inhibits the self-ubiquitination of HDM2 by up-regulation of Akt activity, thereby promoting its protein stability. Moreover, p48 expression leads to accumulated nuclear localization of HDM2, whereas p48 depletion disturbs its nuclear localization. Hence, higher expression of p48 in cancer cells reduces p53 levels through modulation of HDM2 nuclear localization and protein stability via regulation of its Akt-mediated phosphorylation.

Akt2 and nucleophosmin/B23 function as an oncogenic unit in human lung cancer cells.

The signaling network of protein kinase B(PKB)/Akt has been implicated in survival of lung cancer cells. However, understanding the relative contribution of the different isoform of Akt network is nontrival. Here, we report that Akt2 is highly expressed in human lung adenocarcinoma cell line A549 cells. Suppression of Akt2 expression in A549 cells results in notable inhibition of cell poliferation, soft agar growth, and invasion, accompanying by a decrease of nucleophosmin/B23 protein. Overexpression of Akt1 restores cancerous growth of A549 cells in B23-knockdown (KD) cells while Akt2 overexpression did not restore proliferating potential in cells with downregulated B23, thus suggesting Akt2 requires B23 to drive proliferation of lung cancer cell. Loss of functional Akt2 and B23 has similar defects on cell proliferation, apoptotic resistance and cell cycle regulation, while loss of Akt1 has less defects on cell proliferation, survival and cell cycle progression in A549 cells. Moreover, overexpression of B23 rescues the proliferative block induced as a consequence of loss of Akt2. Thus our data suggest that Akt2/B23 functions as an oncogenic unit to drive tumorigenesis of A549 lung cancer cells.

Lactate dehydrogenase as an indicator of severe illness in neonatal intensive care patients: a longitudinal cohort study.

AIM: Lactate dehydrogenase (LDH) increases in several critical conditions that cause cell damage and could potentially be used for early detection of serious illness in the newborn. Our aim was to investigate the relationship between the early clinical course of NICU infants and LDH in plasma at admission. METHODS: LDH was measured in a cohort of patients consecutively admitted to a major NICU in Hanoi. The infants were classified as 'obviously needing intensive care during the first week' (n = 83) or 'not receiving intensive care measures during the first week' (n = 260) by a senior neonatologist blinded to the LDH and lactate activity. RESULTS: LDH differed significantly between the groups in infants born after 32 gestational weeks. LDH differed with the vitality of the patient (F = 26.25, p < 0.0001) at admittance and correlated with lactate (R = 0.496, p < 0.0001). Also, the predictive value for obvious need of intensive care was higher for LDH than for lactate assessed by area under the curve calculated with ROC-curves [0.82 (0.77-0.88) vs. 0.67 (0.60-0.75)]. CONCLUSION: There is a strong relationship between bad clinical condition of infants during first week of life and elevated plasma LDH. The results suggest that LDH might be a valuable support in decision making in the neonatal period.

Nuclear Akt interacts with B23/NPM and protects it from proteolytic cleavage, enhancing cell survival.

B23/NPM is a major nucleolar phosphoprotein that has a critical role in cell proliferation and cell death. Here, we show that it forms a complex with Akt on growth factor (GF) stimulation in both the cytoplasm and the nucleus, for which Akt activation is indispensable. The C terminus of B23 (239-294 residues) potently binds pleckstrin homology (PH) domain of Akt. Akt binding to B23 protects it from proteolytic degradation by caspase-3, leading to the up-regulation of cell survival. Interestingly, unsumoylated B23 K263R, but not wild-type B23, strongly interacts with Akt in the nucleoplasm in the absence of GFs. Furthermore, we show that Akt2, but not other isoforms, specifically regulates B23 sumoylation and protein stability. Also, nuclear Akt regulates the cell cycle progression activity of B23. Therefore, our findings support that nuclear Akt binds and stabilizes B23 in the nucleoplasm, and regulates its activities in cell survival and cell cycle.

Surgery versus conservative care for Rathke's cleft cyst.

BACKGROUND: Rathke's cleft cysts are benign cystic lesions of the sellar region, which may cause headache, pituitary deficiencies and visual disturbances from mass effect. Their management is not standardized yet. This study is about establishing a consensus for medical care of RCC. MATERIAL AND METHODS: We performed a retrospective observational study of all patients that were diagnosed or followed for RCC between 2008 and 2018 (11 years), in the neurosurgical and the adult endocrine departments of our institution. The study's average time length of follow-up is 72.9 months (from 2 to 385 months). RESULTS: The 57 included patients were divided into 2 groups: group A, which included 39 patients that were conservatively managed and group B, which included 18 surgically treated patients. Group A showed either an improvement or a spontaneous resolution of headaches in 56.1% of the cases (P<0.01); a resolution of hyperprolactinemia in 70% of the cases (P=0.21); and of hypogonadism, ACTH deficiency, growth hormone deficiency in 100% of the cases. There was no spontaneous improvement of visual disturbances (P<0.01) or diabetes insipidus (P=0.29) during follow-up. Regarding group B, surgery allowed improvement or complete resolution of headaches in 60% of the cases; visual troubles in 100% of the cases (P<0.01); and hyperprolactinemia in 100% of the cases. Pituitary deficiencies were not improved by surgery. CONCLUSIONS: This study offers guidance in decision-making regarding the management of RCC patients. Surgery is particularly suitable for treating visual disturbances caused by RCC. Regular follow-up is more appropriate than surgery concerning headaches, hyperprolactinemia, endocrine disruptions and diabetes insipidus.

Critical molecular regulators, histomorphometric indices and their correlations in the trabecular bone in primary hip osteoarthritis.

OBJECTIVE: This study examined differential gene expression, histomorphometric indices and relationships between these, in femoral trabecular bone from osteoarthritis (OA) patients and control (CTL) subjects, with the aim of identifying potential molecular drivers consistent with changes in structural and remodelling indices in the OA pathology. MATERIALS AND METHODS: Bone samples from the intertrochanteric (IT) region were obtained from age and sex-matched cohorts of 23 primary hip OA patients and 21 CTL subjects. Real-time polymerase chain reaction (PCR) and histomorphometric analysis were performed on each sample and correlations between gene expression and histomorphometric variables determined. RESULTS: Alterations in gene expression, structural indices and correlations between these were found in OA bone compared to CTL. In OA bone, expression of critical regulators of osteoblast differentiation (TWIST1) and function (PTEN, TIMP4) were decreased, while genes associated with inflammation (SMAD3, CD14) were increased. Bone structural and formation indices (BV/TV, Tb.N, OS/BS) were increased, whereas resorption indices (ES/BS, ES/BV) were decreased. Importantly, significant correlations in CTL bone between CTNNB1 expression and formation indices (OS/BS, OS/BV, OV/BV) were absent in OA bone, indicating altered WNT/ß-catenin signalling. TWIST1 expression and BV/TV were correlated in CTL bone, but not in OA bone, consistent with altered osteoblastogenesis in OA. Matrix metalloproteinase 25 (MMP25) expression and remodelling indices (ES/BS, ES/BV, ES/TV) were correlated only in OA pointing to aberrant bone remodelling in this pathology. CONCLUSIONS: These findings indicate an altered state of osteoblast differentiation and function in OA driven by several key molecular regulators. In association with this differential gene expression, an altered state of both trabecular bone remodelling and resulting microarchitecture were also observed, further characterising the pathogenesis of primary hip OA.

True vasculitis in lupus nephritis.

Vascular lesions are encountered frequently in renal biopsy specimens of patients with systemic lupus erythematosus (SLE) and can present in a variety of morphologic forms. True renal lupus vasculitis (TRLV) is one of the rare vascular lesions associated with lupus nephritis that has been infrequently reported in the medical literature. The primary focus on glomerular pathology and collective classification of the vascular lesions under lupus vasculopathy is one of the reasons why this form of inflammatory vasculitis has been under-recognized as a separate disease entity. Here we have comprehensively reviewed the literature on renal vascular involvement in SLE for a better understanding of the epidemiology, morphologic features, pathogenesis, clinical course and treatment of TRLV. It can be morphologically differentiated from other forms of renal vascular lesions in lupus nephritis, i.e. arteriosclerosis, uncomplicated vascular immune deposits, non-inflammatory necrotizing vasculopathy, and thrombotic microangiopathy. Despite close similarities with antineutrophil cytoplasmic autoantibody associated vasculitis (AASV), there are certain morphological differences that warrant a thorough investigation of the possible pauci-immune mechanism of pathogenesis. The vasculitis follows a severe clinical course in general with rapid progression to renal failure, although favorable outcomes have been reported in certain cases. The standard use of steroids and cytotoxic drugs has yielded variable results in the treatment of TRLV. Current treatment modalities being used in lupus nephritis and AASV have been compared in this article with focus on drugs acting on the inflammatory cells implicated in TRLV pathogenesis.

Tetrahydroxanthone-chromanone heterodimers from lichen Usnea aciculifera and their cytotoxic activity against human cancer cell lines.

Four new tetrahydroxanthone-chromanone heterodimers, usneaxanthones E-H (1-4) together with eleven known compounds (5-15) were isolated from lichen Usnea aciculifera Vain (Parmeliaceae). Their structures and absolute configurations, particularly the central and axial chiralities, were unambiguously demonstrated by a combination of spectroscopic data (1D, 2D NMR, HRESIMS), electronic circular dichroism (ECD) experiments, and single-crystal X-ray crystallographic analyses. The cytotoxicity of new compounds was evaluated on four human cancer cell lines including HCT116 colorectal cancer, MCF-7 breast cancer, A549 lung cancer, and OVCAR-3 ovarian cancer. Compounds 1-4 exhibited good cytotoxicity against all tested cancer cell lines, except ovarian cancer, with the best IC50 value of 3.37 µM. All compounds showed potent cytotoxicity against HCT116 colon cancer with IC50 value from 3.37 to 4.53 µM.

Dimeric tetrahydroxanthones from the lichen Usnea aciculifera.

Four unusual heterodimeric tetrahydroxanthones, usneaxanthones A-D (1-4) were isolated from lichen Usnea aciculifera Vain (Parmeliaceae). Their structures and absolute configurations, particularly the central and axial chiralities, were unambiguously demonstrated by a combination of spectroscopic data (1D, 2D NMR, HRESIMS), electronic circular dichroism (ECD) experiments, and single-crystal X-ray crystallographic analyses. Cytotoxic effects of isolated compounds (1, 2 and 4) were evaluated on HT-29 human colorectal cancer cells. Compound 4 showed potent cytotoxicity against HT-29 with IC50 values of 2.41 µM.

Development of experimental model of chronic pyelonephritis with Escherichia coli O75:K5:H-bearing Dr fimbriae: mutation in the dra region prevented tubulointerstitial nephritis.

Escherichia coli that express Dr fimbriae and related adhesins recognize the common receptor decay accelerating factor. E. coli strains that express adhesins of the Dr family were postulated to be associated with cystitis (30-50%), pregnancy-associated pyelonephritis (30%), and chronic diarrhea (50%). In this study, we investigated the hypothesis that E. coli renal interstitial binding mediated by the Dr adhesin may be important for the development of chronic pyelonephritis. An insertional dra mutant, E. coli DR14, of the clinical E. coli isolate IH11128 bearing Dr fimbriae, was constructed and used to characterize persistence of infection and interstitial tropism in an experimental model of ascending pyelonephritis. Quantitative cultures of kidney homogenates indicated that Dr hemagglutinin positive (Dr+) E. coli IH11128 established a 1-yr colonization of renal tissue. In the Dr hemagglutinin negative (Dr-) group, 50% of animals cleared infection within 20 wk and 100% between 32 to 52 wk. Dr+ E. coli colonized the renal interstitium. Significant histological changes corresponding to tubulointerstitial nephritis including interstitial inflammation, fibrosis, and tubular atrophy were found in the kidney tissue of the Dr+ but not the Dr- group. A substantial amount of fimbrial antigen was detected in the parenchymal regions affected by interstitial inflammation and fibrosis. The obtained results are consistent with the hypothesis that mutation within the dra region, affecting E. coli binding to tubular basement membranes, prevented renal interstitial tropism and the development of the changes characteristically seen in tubulointerstitial nephritis.

Adenoviral delivery of E2F-1 directs cell cycle reentry and p53-independent apoptosis in postmitotic adult myocardium in vivo.

Irreversible exit from the cell cycle precludes the ability of cardiac muscle cells to increase cell number after infarction. Using adenoviral E1A, we previously demonstrated dual pocket protein- and p300-dependent pathways in neonatal rat cardiac myocytes, and have proven that E2F-1, which occupies the Rb pocket, suffices for these actions of E1A. By contrast, the susceptibility of adult ventricular cells to viral delivery of exogenous cell cycle regulators has not been tested, in vitro or in vivo. In cultured adult ventricular myocytes, adenoviral gene transfer of E2F-1 induced expression of proliferating cell nuclear antigen, cyclin-dependent protein kinase 4, cell division cycle 2 kinase, DNA synthesis, and apoptosis. In vivo, adenoviral delivery of E2F-1 by direct injection into myocardium induced DNA synthesis, shown by 5'-bromodeoxyuridine incorporation, and accumulation in G2/M, by image analysis of Feulgen-stained nuclei. In p53(-)/- mice, the prevalence of G1 exit was more than twofold greater; however, E2F-1 evoked apoptosis and rapid mortality comparably in both backgrounds. Thus, the differential effects of E2F-1 on G1 exit in wild-type versus p53-deficient mice illustrate the combinatorial power of viral gene delivery to genetically defined recipients: E2F-1 can override the G1/S checkpoint in postmitotic ventricular myocytes in vitro and in vivo, but leads to apoptosis even in p53(-)/- mice.

Developing a preclinical model of Parkinson's disease: a study of behaviour in rats with graded 6-OHDA lesions.

Injection of increasing concentrations of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle (MFB) can be used to establish a graded model of different clinical stages of Parkinson's disease (PD). We investigated the relationship between behavioural alterations and loss of dopaminergic neurons in the substantia nigra pars compacta (SNc). Forty female Sprague-Dawley rats were injected with either (i) 4 microg (ii) 8 microg or (iii) 16 microg 6-hydroxydopamine (6-OHDA) to mimic the preclinical, mild and advanced clinical stages of PD, respectively. Vehicle was injected in a separate control group. Behaviours analysed included postural asymmetry, balance, locomotion, sensorimotor deficits and apomorphine rotation. At post-mortem the degree of tyrosine immunoreactive dopaminergic cell (TH-ir) loss was then estimated. There was a graded and consistent trend in each of the behaviours studied with respect to cell loss between the different sized lesion groups when examined using correlation analysis (all comparisons, r > 0.8, p < 0.001). Rats with large lesions demonstrated more significant behavioural changes over 8 weeks of testing than those with intermediate and smaller lesions (group comparisons p < 0.001). PD symptomatology became overt when cell loss reached 70%, however some significant changes can be observed with as little as 40% dopaminergic cell loss. Thus, injection with increasing concentrations 6-OHDA into the MFB can produce increasing extents of cell loss and behavioural changes, which were well correlated. This graded model can be useful for testing potential neuroprotective compounds for PD.

Caveolin-1 expression in clinically confined human prostate cancer: a novel prognostic marker.

We demonstrated previously elevated caveolin-1 expression in metastatic mouse and human prostate cancer cells both in vitro and in vivo. In this study, we analyzed its prognostic value for progression of clinically confined human prostate cancer. Immunohistochemical staining with a caveolin-1-specific antibody was performed on routinely processed paraffin sections from 189 radical prostatectomy specimens. Caveolin-1 immunoreactivity was evaluated in association with patients' age, race, preoperative prostate-specific antigen, clinical stage, and pathological features including Gleason score, extraprostatic extension, status of surgical margins, and time to disease progression after surgery. Positive caveolin-1 immunostaining was detected in 47 of the 189 cancers (25%) and correlated positively with Gleason score, positive surgical margin, as well as lymph node involvement (P = 0.0071, 0.0267, and 0.0399, respectively). In lymph node-negative cancers (n = 162), caveolin-1 immunoreactivity predicts a shorter time to disease progression after surgery (P = 0.0033, univariate analysis). Multivariate analyses that included caveolin-1 and other prognostic pathological markers identified positive caveolin-1 immunostaining as an independent predictor for time to disease progression (P = 0.0186). Thus, our study establishes caveolin-1 as a novel prognostic marker for clinically confined human prostate cancer.

Persistence of detectable insecticidal proteins from Bacillus thuringiensis (Cry) and toxicity after adsorption on contrasting soils.

Insecticidal Cry, or Bt, proteins are produced by the soil-endemic bacterium, Bacillus thuringiensis and some genetically modified crops. Their environmental fate depends on interactions with soil. Little is known about the toxicity of adsorbed proteins and the change in toxicity over time. We incubated Cry1Ac and Cry2A in contrasting soils subjected to different treatments to inhibit microbial activity. The toxin was chemically extracted and immunoassayed. Manduca sexta was the target insect for biotests. Extractable toxin decreased during incubation for up to four weeks. Toxicity of Cry1Ac was maintained in the adsorbed state, but lost after 2 weeks incubation at 25 °C. The decline in extractable protein and toxicity were much slower at 4 °C with no significant effect of soil sterilization. The major driving force for decline may be time-dependent fixation of adsorbed protein, leading to a decrease in the extraction yield in vitro, paralleled by decreasing solubilisation in the larval gut.

Clustered p53 immunostaining: a novel pattern associated with prostate cancer progression.

Abnormal p53 protein accumulation is typically defined as present when greater than 5 or 10% of cancer cells stain positively. We present a novel approach whereby immunopositivity is defined when 15 or more cells within a 300 x 400-micrometer(2) field exhibit p53 protein accumulation; a feature that we have called "clustered" staining. We assessed p53 immunostaining of moderately differentiated, clinically localized prostate cancers derived from two patient groups: those without cancer recurrence 5 years after radical prostatectomy, and those in whom cancer had recurred following radical prostatectomy. Clustered p53 immunopositivity was present in 10 (63%) of 16 patients in the recurrent group and in only 7 (21%) of 33 in the nonrecurrent group. Clustered p53 staining was clearly associated with cancer recurrence (P < 0.01). This refinement of a commonly used assay may help define the biological aggressiveness of a cancer.

Reduced levels of transforming growth factor beta receptor type II in human prostate cancer: an immunohistochemical study.

In previous studies we demonstrated that the growth of human prostatic adenocarcinoma is associated with aberrant accumulation of transforming growth factor (TGF) beta1, a growth factor that has been shown to be a potent inhibitor of epithelial cell proliferation. We investigated the expression of TGF-beta receptor II (TGFbetaR-II) in benign prostate tissue and in prostate cancer using standard immunohistochemical techniques. Quantitation of immunopositivity for TGFbetaR-II was assessed on a visual analogue scale ranging from 0 (absence of staining) to 4+ (intensely positive staining). All of the benign glandular epithelia stained intensely, either 3+ or 4+, representative of the ubiquitous nature of TGFbetaR-II in normal tissue. Overall, staining was reduced in prostate cancer sections, and there was progressively diminished staining as the histological grade of the cancer increased (P < 0.01, Kruskal-Wallis test). This immunohistochemical study indicates that a decline in the levels of TGFbetaR-II is correlated with advancing histological aggressiveness of the cancer and suggests that aberrant TGFbetaR-II function may play a role in human prostate carcinogenesis.

Elevated expression of caveolin is associated with prostate and breast cancer.

To identify genes associated with prostate cancer progression, we developed a strategy involving the use of differential display-PCR with a panel of genetically matched primary tumor- and metastasis-derived mouse prostate cancer cell lines. We isolated a cDNA fragment with homology to the mouse caveolin-1 gene. Northern blotting with this fragment revealed increased caveolin expression in metastasis-derived cell lines relative to primary tumor-derived cell lines. Western blotting with a polyclonal caveolin antibody confirmed increased caveolin protein in metastasis-derived mouse cell lines and expression in three of four human prostate cancer cell lines. Immunohistochemical analysis of a human prostate cancer cell line demonstrated a prominent granular pattern of caveolin accumulation. Subsequent analysis of mouse and human prostate specimens revealed minimal caveolin expression in normal epithelium with abundant staining of smooth muscle and endothelium. The frequency of caveolin-positive cells was increased in prostate cancer with markedly increased accumulation of caveolin and a granular staining pattern in lymph node metastatic deposits. In human breast cancer specimens, increased caveolin staining was detected in intraductal and infiltrating ductal carcinoma as well as nodal disease. Caveolin therefore appears to be associated with human prostate cancer progression and is also present in primary and metastatic human breast cancer.

Mesenchymal-epithelial interactions and transforming growth factor-beta expression during mouse prostate morphogenesis.

To explore the role of transforming growth factor-beta (TGF beta) isoforms and other growth-related genes during prostate morphogenesis in the mouse, we examined mRNA levels in fetal day 17 urogenital sinus, mesenchyme (UGM), and epithelium (UGE) as well as in the ventral, dorsal, and anterior lobes of the adult prostate. In addition, we used antiserum specific for extracellular TGF beta 1 in immunohistochemical studies to localize accumulation of the TGF beta 1 isozyme in the above tissues as well as those derived from fetal day 19 and neonatal mouse prostate. Differential patterns of expression in fetal and adult tissues were seen. TGF beta 1, -beta 2, and -beta 3 expression was substantially elevated in UGM compared to that in UGE, yet only TGF beta 1, not TGF beta 2 or TGF beta 3, mRNA levels were sustained in adult prostate tissues. High levels of accumulation of TGF beta 1 were demonstrated by immunohistochemistry in the mesenchymal compartment compared to those in the epithelial compartment throughout development. Interestingly, the highest levels of TGF beta 1 appeared in areas of active epithelial duct formation and delineated the mesenchymal architectural changes necessary for ductal network formation. Additional studies revealed that levels of mRNAs for other genes involved in tissue remodeling and growth were also elevated in UGM compared to those in UGE. Tissue plasminogen activator, urokinase plasminogen activator, androgen receptor, and c-myc mRNA levels were also elevated in UGM compared to UGE. Interestingly, whereas tissue plasminogen activator mRNA levels, like those of TGF beta 2 and -beta 3, were barely detectable in adult prostatic tissues, mRNA levels for urokinase plasminogen activator, androgen receptor, and c-myc were readily detected and expressed in a lobe-specific fashion. Overall, these data indicate that expression of TGF beta 1 isoforms and other growth-related genes is associated with mesenchymal cells in areas of active morphogenesis during prostate development and provide objective molecular and cellular information regarding mediators of mesenchymal-epithelial interactions in prostate.

Acute myelofibrosis. A report of four cases and review of the literature.

Four new cases of acute myelofibrosis are reported, and 63 cases reported in the literature are reviewed. The typical features of this disease include a rapidly progressive clinical course; nonspecific symptoms such as weight loss, anorexia, fatigue and weakness; the absence of organomegaly; pancytopenia; circulating blast cells; and mild abnormalities in the red blood cell morphology. The bone marrow aspirates are usually "dry." The bone marrow biopsies are essential for the diagnosis and show four consistent features: hypercellularity, reticulin fibrosis, proliferation of blast cells and bizarre, atypical megakaryocytes. In 16 cases, the blast cells in peripheral blood and bone marrow, which are unclassifiable by conventional morphology, could be identified as megakaryoblasts by ultrastructural and immunocytochemical techniques. It is concluded that acute myelofibrosis is a definite clinicopathologic entity, which may be related to acute megakaryoblastic leukemia.