Successful treatment of hemophagocytic lymphohistiocytosis in a patient with systemic lupus erythematosus with ruxolitinib: a case report.

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening hematological disorder characterized by uncontrolled activation of CD8+ T and natural killer cells, leading to a cytokine storm and severe organ dysfunction. Although secondary HLH related to autoimmune diseases usually demonstrates a good treatment response to immunosuppressive therapy for underlying conditions, there is no consensus regarding the treatment in case of unresponsiveness to the treatment. Herein, we present a case of HLH that was unresponsive to high-dose glucocorticoid and cyclosporine treatment in a patient with newly diagnosed systemic lupus erythematosus. The patient's clinical features and laboratory abnormalities rapidly improved with ruxolitinib, an oral Janus kinase 1 and 2 (JAK1/2) inhibitor. This result suggests that blocking JAK-STAT pathway may be a potential treatment option in patients with refractory HLH secondary to autoimmune diseases.

Balloon neck-plasty to create a wide-necked aneurysm in the elastase-induced rabbit model.

PURPOSE: The elastase-induced aneurysm (EIA) model in rabbits has been proposed for translational research; however, the adjustment of aneurysm neck size remains challenging. In this study, the technical feasibility and safety of balloon neck-plasty to create a wide-necked aneurysm in rabbit EIA model were investigated. METHODS: Male New Zealand White rabbits (N = 15) were randomly assigned to three groups: group A, EIA creation without neck-plasty; group B, neck-plasty immediately after EIA creation; group C, neck-plasty 4 weeks after EIA creation. The diameter of balloon used for neck-plasty was determined 1 mm larger than origin carotid artery diameter. All rabbits were euthanized 4 weeks after their final surgery. Aneurysm neck, height, dome-to-neck (D/N) ratio, and histologic parameters were compared among the groups. RESULTS: Aneurysm creation was technically successful in 14 out of 15 rabbits (93.3%), with one rabbit experiencing mortality due to an adverse anesthetic event during the surgery. Saccular and wide-necked aneurysms were successfully created in all rabbits. Aneurysm neck was significantly greater in groups B and C compared to group A (all P < .05). D/N ratio was significantly lower in groups B and C compared to group A (all P < .05). Additionally, tunica media thickness, vessel area, and luminal area were significantly greater in groups B and C compared to group A (all P < .05). These variables were found to be significantly greater in group B compared to group C (all P < .05). CONCLUSION: The creation of a wide-necked aneurysm using balloon neck-plasty after elastase induction in rabbits has been determined to be technically feasible and safe.

Modeling of antibody responses to COVID-19 vaccination in patients with rheumatoid arthritis.

To construct a model of the antibody response to COVID-19 vaccination in patients with rheumatoid arthritis (RA), and to identify clinical factors affecting the antibody response. A total of 779 serum samples were obtained from 550 COVID-19-naïve RA patients who were vaccinated against COVID-19. Antibody titers for the receptor binding domain (anti-RBD) and nucleocapsid (anti-N) were measured. The time from vaccination, and the log-transformed anti-RBD titer, were modeled using a fractional polynomial method. Clinical factors affecting antibody responses were analyzed by a regression model using generalized estimating equation. The anti-RBD titer peaked at about 2 weeks post-vaccination and decreased exponentially to 36.5% of the peak value after 2 months. Compared with the first vaccination, the 3rd or 4th vaccinations shifted the peaks of anti-RBD antibody response curves significantly upward (by 28-fold [4-195] and 32-fold [4-234], respectively). However, there was no significant shift in the peak from the 3rd vaccination to the 4th vaccination (p = 0.64). Multivariable analysis showed that sulfasalazine increased the vaccine response (by 1.49-fold [1.13-1.97]), but abatacept or JAK inhibitor decreased the vaccine response (by 0.13-fold [0.04-0.43] and 0.44-fold [0.26-0.74], respectively). Age was associated with lower ln [anti-RBD] values (coefficient: - 0.03 [- 0.04 to - 0.02]). In conclusion, the anti-RBD response of RA patients peaked at 2 weeks after COVID-19 vaccination, and then decreased exponentially, with the maximum peak increase observed after the 3rd vaccination. The antibody response was affected by age and the medications used to treat RA.

Impact of a selective lens dose reduction protocol in 3D rotational angiography on radiation exposure to the eye lens during cerebral angiography: a randomized controlled trial.

BACKGROUND: We aimed to investigate the radiation dose to the eye lens (lens dose) during cerebral angiography and to evaluate the effectiveness of the lens dose reduction protocol for 3-dimensional rotational angiography (3D-RA) in reducing overall lens dose exposure. METHODS: We conducted a randomized, controlled clinical trial at a tertiary hospital with patients undergoing cerebral angiography. The lens dose reduction protocol in 3D-RA involved raising the table to position the patient's eye lens away from the rotation axis. The lens dose was estimated by measuring the entrance surface air kerma using a photoluminescent glass dosimeter. The lens doses of 3D-RA, overall examination, and image quality were analyzed and compared between the two groups. RESULTS: A total of 20 participants (mean age, 58±9.4 years; including 12 men [60%]) were enrolled and randomly assigned to either the conventional group or the dose reduction group. The median lens dose in 3D-RA was significantly lower in the dose reduction group compared with the conventional group (1.1 mGy vs 4.5 mGy, p<0.001). The total dose was significantly lower in the dose reduction group (median of 7.5 mGy vs 10.2 mGy, p=0.003). In the conventional group, 3D-RA accounted for 46% of the total lens dose, while in the dose reduction group, its proportion decreased to 16%. No significant differences were observed in the image quality between the groups. CONCLUSION: The lens dose reduction protocol resulted in a significant reduction in the lens dose of the 3D-RA as well as entire cerebral angiography, while maintaining the image quality.

Reduction of Radiation Dose to Eye Lens in Cerebral 3D Rotational Angiography Using Head Off-Centering by Table Height Adjustment: A Prospective Study.

OBJECTIVE: Three-dimensional rotational angiography (3D-RA) is increasingly used for the evaluation of intracranial aneurysms (IAs); however, radiation exposure to the lens is a concern. We investigated the effect of head off-centering by adjusting table height on the lens dose during 3D-RA and its feasibility in patient examination. MATERIALS AND METHODS: The effect of head off-centering during 3D-RA on the lens radiation dose at various table heights was investigated using a RANDO head phantom (Alderson Research Labs). We prospectively enrolled 20 patients (58.0 ± 9.4 years) with IAs who were scheduled to undergo bilateral 3D-RA. In all patients' 3D-RA, the lens dose-reduction protocol involving elevation of the examination table was applied to one internal carotid artery, and the conventional protocol was applied to the other. The lens dose was measured using photoluminescent glass dosimeters (GD-352M, AGC Techno Glass Co., LTD), and radiation dose metrics were compared between the two protocols. Image quality was quantitatively analyzed using source images for image noise, signal-to-noise ratio, and contrast-to-noise ratio. Additionally, three reviewers qualitatively assessed the image quality using a five-point Likert scale. RESULTS: The phantom study showed that the lens dose was reduced by an average of 38% per 1 cm increase in table height. In the patient study, the dose-reduction protocol (elevating the table height by an average of 2.3 cm) led to an 83% reduction in the median dose from 4.65 mGy to 0.79 mGy (P < 0.001). There were no significant differences between dose-reduction and conventional protocols in the kerma area product (7.34 vs. 7.40 Gy·cm², P = 0.892), air kerma (75.7 vs. 75.1 mGy, P = 0.872), and image quality. CONCLUSION: The lens radiation dose was significantly affected by table height adjustment during 3D-RA. Intentional head off-centering by elevation of the table is a simple and effective way to reduce the lens dose in clinical practice.

Risk of Bloodstream Infection in Patients with Systemic Lupus Erythematosus Exposed to Prolonged Medium-to-High-Dose Glucocorticoids.

OBJECTIVES: This study aimed to investigate the incidence rate and risk factors of bloodstream infection (BSI) in patients with systemic lupus erythematosus (SLE) exposed to medium to high doses of glucocorticoids. METHODS: This study included 1109 treatment episodes with prolonged (≥4 weeks) medium-to-high-dose glucocorticoids (≥15 mg/day prednisolone) in 612 patients with SLE for over 14 years. Clinical features regarding systemic lupus erythematosus disease activity index 2000 (SLEDAI-2K), immunosuppressant use, and laboratory results were obtained from the electronic medical database. The primary outcome of this study was the 1-year incidence of BSI. The effect of clinical factors on the outcome was investigated using a generalized estimating equation. RESULTS: During a total of 1078.64 person-years, 30 cases of BSI occurred, with an incidence rate of 2.78 (95% confidence interval (CI) 1.88-3.97) per 100 person-years. Mortality rate of the treatment episodes with BSI was 16.7%, which was significantly higher than that in the other episodes (incidence rate ratio (IRR) 19.59, 95% CI 7.33-52.44). When the incidence rate of BSI was stratified by baseline glucocorticoid dose and SLEDAI-2K score, a higher incidence rate of BSI occurred as disease activity or baseline glucocorticoid dose increased. In the multivariable analysis, SLEDAI-2K ≥20 (adjusted IRR (aIRR) 4.66, 95% CI 2.17-10.00), initial baseline prednisolone ≥ 60 mg/day (aIRR 2.42, 95% CI 1.11-5.32), and cumulative prednisolone dose ≥15 mg/day during the previous 6 months (aIRR 2.13, 95% CI 1.03-4.40) significantly increased the risk of BSI. CONCLUSION: In patients with SLE exposed to prolonged medium-to-high-dose glucocorticoids, the 1-year incidence rate of BSI was significantly higher than previously reported in the general patients with SLE. Severe disease activity, and high-dose glucocorticoid treatment previously or at baseline increased the risk of BSI.

Feasibility of a silicone vascular phantom replicating real arterial contrast filling dynamics on cerebral angiography: An in-vitro pilot study.

Some cerebral arterial silicone phantoms have been used in preclinical evaluations. However, typical silicone-based phantoms are limited in their capacity to reproduce real contrast filling dynamics of the human cerebral artery. This study aimed to develop a cerebral arterial silicone phantom to analyze the feasibility of real contrast filling dynamics. The fluid circulation phantom system consisted of a cerebral arterial silicone phantom without or with additional devices, a pump, an injection system, a pressure-monitoring system, a constant-temperature bath, and a venous drainage container. Vascular resistance was reproduced with a plastic cistern only or a plastic cistern filled with a sponge pad. Three phantom groups were constructed as follows: a) the cerebral arterial silicone phantom used as the control group (type A), b) phantom with the incorporated plastic cistern (type B), and c) phantom with the incorporated plastic cistern filled with a sponge pad (type C). The contrast concentration-time curve patterns of the three groups obtained from digital subtraction angiography (DSA) were compared. Consequently, the DSA pattern of the type C phantom was the most similar to that obtained from the control group as the reference data, which showed the broadest full-width-at-half-maximum and the area under the curve values and the highest maximum contrast concentration. In conclusion, we could emulate the arterial contrast filling dynamics of clinical cerebral angiography by applying a small cistern filled with a sponge pad at the drainage side of the phantom.

A modified method of elastase-induced saccular aneurysm creation in rabbits: Schematic representation of the method.

BACKGROUND: The purpose of our study was to investigate the safety and effectiveness of a modified technique using a short guiding catheter for instillation of elastase in comparison with the previously described method of creating elastase-induced aneurysm in rabbits. METHODS: Following right common carotid artery (RCCA) access using an arterial sheath and inflating the Fogarty balloon in the subclavian artery, a short guiding catheter was used for the instillation of the elastase in the experimental group (n = 5) while it was performed with a microcatheter in the control group (n = 5). The procedure duration was recorded from the RCCA puncture to the sheath removal. The histological changes were characterized using H&E and Masson's trichrome (MT) staining. RESULTS: The procedure time was 23 ± 2 min in the experimental group and 29 ± 2 min in the control group. All the rabbits (100%) in the experimental group survived without neurologic deficits, but two rabbits (40%) survived in the control group. All aneurysms were created in the saccular shape (100%) with a neck size of 2.3 ± 0.29 mm, a width of 2.75 ± 0.36 mm, and height of 6.37 ± 0.46 mm, and a dome to neck ratio of 1.21 ± 0.23. The aneurysm walls were partly thickened due to the degradation of the media tunica and adventitia proliferation with loss of the internal elastic lamina. CONCLUSION: By using a short guiding catheter, we could instill the elastase in a more effective and safe manner in the creation of the elastase-induced aneurysm model in rabbits.

Trends of Expanding Indications of Woven EndoBridge Devices for the Treatment of Intracranial Aneurysms: A Systematic Review and Meta-analysis.

PURPOSE: Woven EndoBridge (WEB) was introduced for the endovascular therapy of wide-neck intracranial aneurysms. The safety and efficacy have been evaluated through several meta-analyses. However, these reviews did not cover the expanding indications in detail. Therefore, we aimed to show the changing trends for intracranial aneurysm treatment using the WEB device. METHODS: A systematic review and meta-analysis was conducted with PubMed, Embase, and Cochrane databases. We searched for studies that reported baseline characteristics of aneurysms and the WEB devices, which had treated more than 20 aneurysms consecutively. The pooled proportions of aneurysm indications and used WEB device types were obtained. To evaluate the changing indications for the treated aneurysm size, including the neck diameter, a trend line and linear regression model was measured. RESULTS: A total of 27 cohorts were included encompassing 1831 aneurysms treated with the WEB. A total of 86% were used in the four major locations as on-label indications (middle cerebral artery bifurcation; 34%, anterior communicating artery; 26%, basilar tip; 18%, internal carotid artery terminus; 7%). Among off-label indications, the most common location was the posterior communicating artery (8%), followed by the anterior cerebral artery including the pericallosal artery (6%). The median aneurysm size and neck diameter was 7 mm and 4.6 mm, respectively. The WEB device has been used for the treatment of smaller aneurysms than the initial indication. Also, the proportion for ruptured aneurysm treatment was increased up to 15%. CONCLUSION: The mechanical and technical development of the WEB resulted in expanding the indications for the treatment of intracranial aneurysms. The off-label indications accounted for 14% in total and an increasing number of small aneurysms are treated with WEB devices. Moreover, the proportion for ruptured aneurysm treatment was currently increased up to 14% more than in the beginning.

A Multicenter, Prospective, Randomized, Parallel-Group Trial on the Effects of Temporary Methotrexate Discontinuation for One Week Versus Two Weeks on Seasonal Influenza Vaccination in Patients With Rheumatoid Arthritis.

OBJECTIVE: This clinical trial was conducted to investigate whether discontinuing methotrexate (MTX) for 1 week after seasonal influenza vaccination is noninferior to discontinuing for 2 weeks after vaccination in patients with rheumatoid arthritis (RA). METHODS: In this multicenter, prospective, randomized, parallel-group noninferiority trial, RA patients receiving a stable dose of MTX were randomly assigned at a ratio of 1:1 to discontinue MTX for 1 week or for 2 weeks after they received the quadrivalent 2021-2022 seasonal influenza vaccine containing H1N1, H3N2, B/Yamagata, and B/Victoria strains. The primary outcome measure was the proportion of patients with a satisfactory vaccine response, which was defined as ≥4-fold increase in antibody titers, as determined with the hemagglutination inhibition assay, against ≥2 of the 4 vaccine strains at 4 weeks after vaccination. RESULTS: The modified intent-to-treat population included 90 patients in the 1-week MTX hold group and 88 patients in the 2-week MTX hold group. The mean ± SD MTX doses were 12.6 ± 3.4 mg/week in the 1-week MTX hold group and 12.9 ± 3.3 mg/week in the 2-week MTX hold group. The proportion of satisfactory vaccine responses did not differ between the groups (68.9% versus 75.0%; P = 0.364). The rate of seroprotection and the fold increase in antibody titers for each of the 4 influenza antigens were similar between the groups. CONCLUSION: A temporary discontinuation of MTX for 1 week after vaccination was noninferior to a discontinuation of MTX for 2 weeks after vaccination, regarding induction of a satisfactory vaccine response to a seasonal influenza vaccine in patients with RA receiving a stable dose of MTX.

Endovascular Treatment of Arterial Steno-Occlusive Lesions in Symptomatic Moyamoya Disease.

The efficacy and safety of endovascular treatment (EVT) for moyamoya disease (MMD) have rarely been investigated. The objective of this study was to summarize the clinical outcomes of EVT for MMD and determine the potential role of EVT in treating symptomatic steno-occlusive lesions in MMD. Reports from January 2000 to December 2021 describing EVT in MMD were collected through a literature search. The search terms included "moyamoya", "stent", "angioplasty", and "endovascular". Data regarding baseline demographics, previous medical history, treated vessel, periprocedural complications, and angiographical recurrence were retrieved. This review included 10 studies with details of 19 patients undergoing a total of 31 EVT procedures. Twenty-one EVTs were performed as initial treatments for MMD, and 10 were performed as additional treatments for angiographical recurrence. The mean follow-up period of the initial EVTs was 9.0±11.9 months, with angiographical recurrence in 11 (68.8%) cases. The mean follow-up period of additional EVTs was 4.3±3.9 months, and seven (70.0%) EVTs showed restenosis of the re-treated vessel. Across all initial and additional EVTs, there were no differences in characteristics between the recurrence and non-recurrence groups. Overall, two periprocedural complications (9.5%) occurred, one vessel rupture and one massive intracerebral hemorrhage with subarachnoid hemorrhage. EVT plays a limited role in the management of symptomatic intracranial arterial steno-occlusive lesions of MMD. Recent advances in understanding the pathomechanism of MMD may urge neuro-interventionists to find a new endovascular approach with better balloon angioplasty or stenting mechanisms.

Utility of the breath-holding test in patients with systemic sclerosis.

OBJECTIVES: Cardiopulmonary involvement is a major cause of death in patients with SSc. This study evaluated the clinical utility and reliability of breath-holding test (BHT) in evaluating cardiopulmonary function in patients with SSc. METHODS: Seventy-two prospectively enrolled patients with SSc underwent BHT and the 6 min walk test (6MWT), along with measurements of the Borg dyspnoea scale and Scleroderma Health Assessment Questionnaire (SHAQ). Data on pulmonary function test and echocardiography were also collected. Validity was assessed based on the correlations between the best BHT and relevant clinical parameters. To assess the reliability of BHT, an additional 31 patients with SSc underwent BHTs twice within 2 week intervals. RESULTS: Mean (s.d.) best BHT time was 38.4 (15.7) s, and 6MWT distance was 473.5 (95.5) m. BHT showed significant correlations with the Borg dyspnoea scale before (r = -0.367, P < 0.001) and after (r = -0.285, P = 0.016) testing, whereas 6MWT were correlated with the Borg dyspnoea scale after (r = -0.351, P = 0.002) but not before (r = -0.113, P = 0.343) testing. BHT time was correlated with diffusing capacity for carbon monoxide (%, r = 0.426, P < 0.001), forced vital capacity (litres, r = 0.373, P = 0.001), pulmonary arterial systolic pressure (mmHg, r = -0.272, P = 0.031) and SHAQ score (r = -0.470, P < 0.001), but not with left ventricular ejection fraction (%, r = -0.135, P = 0.263). BHT showed excellent reliability, with an intraclass correlation coefficient (2, 1) of 0.943 (95% CI: 0.88, 0.97). CONCLUSION: BHT, a simple and less time-consuming test, shows excellent reliability and significant correlation with the Borg scale, SHAQ and pulmonary parameters. These results suggest that BHT might be a useful surrogate marker of pulmonary capacity in SSc patients. TRIAL REGISTRATION NUMBER: NCT04484948.

SR-5, the specific ratio of Korean multi-herbal formula: An evaluation of antiulcerogenic effects on experimentally induced gastric ulcers in mice.

PURPOSE: Previously, we demonstrated that the specific ratio of Korean multi-herbal formula (SR-5) exhibits hepatoprotective properties against ethanol-induced hepatic damage in rats. Chronic and excessive alcohol consumption is a major etiological factor involved in gastric disease and ulcer development induced by the inflammatory response and oxidative stress. METHODS: The present study evaluated the gastroprotective effects of SR-5 (100, 150, and 200 mg/kg) against hydrochloride acid/ethanol (HCl/EtOH)-induced and indomethacin/hydrochloride acid (INDO/HCl)-induced gastritis in a mouse model and the mechanisms involved. RESULTS: All the tested doses of SR-5 significantly inhibited gastric lesions in the HCl/EtOH-induced ulcer model mice. Similarly, all the tested doses of SR-5 significantly inhibited gastric lesions in the INDO/HCl-induced ulcer model mice. Furthermore, mice pretreated with SR-5 had significantly increased gastric levels of enzymatic and nonenzymatic antioxidants, namely, catalase (CAT) and glutathione (GSH), with concomitant reductions in malondialdehyde (MDA) and reactive oxygen species (ROS) levels compared with those in the HCl/EtOH or INDO/HCl group. SR-5 suppressed the expression of nuclear factor-kappa B (NF-κB)/p65, inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α), and cyclooxygenase-2 (COX-2) to their normal values. CONCLUSION: These findings are the first to demonstrate the powerful protective effect of SR-5 against gastric injury development and provide hope for clinical application.

A case of dermatomyositis in a patient with central core disease: unusual association with autoimmunity and genetic muscle disease.

BACKGROUND: Dermatomyositis is an inflammatory muscle disease caused by immune-mediated muscle injury, and central core disease (CCD) is a congenital myopathy associated with disturbed intracellular calcium homeostasis and excitation-contraction coupling. To date, CCD has not been reported to have autoantibodies or coexist with inflammatory myopathy. CASE PRESENTATION: Here, we described the case of a 25-year-old woman who had progressive proximal muscle weakness, myalgia, pruritic macular rash, skin ulcers, and calcinosis. Dermatomyositis was initially suspected based on the clinical symptoms accompanied by elevated muscle enzyme levels, electromyography abnormalities, and a positive antinuclear antibody test. However, the patient's muscle biopsy revealed the characteristic findings of both dermatomyositis and CCD, suggesting that dermatomyositis occurred in this patient with previously asymptomatic CCD. The patient did not have any pathogenic gene mutations associated with congenital myopathy, including RYR1 and SEPN1 in targeted next-generation sequencing. She received high-dose glucocorticoid therapy and azathioprine with a significant improvement in muscle strength. CONCLUSIONS: We present a case of rare coexistence of dermatomyositis and CCD. Clinicians should be aware that patients with CCD may have inflammatory myopathy that responds well to immunosuppressive therapy.

A Case of Overlap Syndrome of Systemic Sclerosis and Cryoglobulinemic Vasculitis With Central Nervous System Involvement.

Mixed cryoglobulinemic vasculitis (CV) is occasionally caused by autoimmune diseases including systemic sclerosis. Multiorgan involvement such as skin, kidney, and peripheral nerve involvement is common in mixed CV. However, central nervous system (CNS) involvement is extremely rare. Here, we report a case of overlap syndrome of limited cutaneous systemic sclerosis and mixed cryoglobulinemic vasculitis with CNS involvement. The neurologic deficits and systemic symptoms improved promptly after steroid and cyclophosphamide therapy.

Analysis of the Active Constituents and Evaluation of the Biological Effects of Quercus acuta Thunb. (Fagaceae) Extracts.

We evaluated the antioxidant and antibacterial activity of hexnane, ethyl acetate, acetone, methanol, ethanol, and water extracts of the Quercus acuta leaf. The antioxidant properties were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, reducing power, and total phenolic content. Antibacterial activity was assessed against general infectious pathogens, including antibiotic-resistant clinical isolates. The methanolic extract showed the highest DPPH radical scavenging activity and total phenolic content, while the reducing power was the highest in the water extract. The ethyl acetate extract showed the best antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) strains. Additionally, it displayed antibacterial activity against Staphylococcus aureus KCTC1928, Micrococcus luteus ATCC 9341, Salmonella typhimurium KCTC 1925, Escherichia coli KCTC 1923, and eight MRSA strains. These results present basic information for the possible uses of the ethanolic and ethyl acetate extracts from Q. acuta leaf in the treatment of diseases that are caused by oxidative imbalance and antibiotic-resistant bacterial infections. Six active compounds, including vitamin E, which are known to possess antioxidant and antibacterial activity, were identified from the extracts. To the best of our knowledge, this is the first study that reports the chemical profiling and antibacterial effects of the various QA leaf extracts, suggesting their potential use in food therapy or alternative medicine.

Comprehensive evaluation of matrix factorization methods for the analysis of DNA microarray gene expression data.

BACKGROUND: Clustering-based methods on gene-expression analysis have been shown to be useful in biomedical applications such as cancer subtype discovery. Among them, Matrix factorization (MF) is advantageous for clustering gene expression patterns from DNA microarray experiments, as it efficiently reduces the dimension of gene expression data. Although several MF methods have been proposed for clustering gene expression patterns, a systematic evaluation has not been reported yet. RESULTS: Here we evaluated the clustering performance of orthogonal and non-orthogonal MFs by a total of nine measurements for performance in four gene expression datasets and one well-known dataset for clustering. Specifically, we employed a non-orthogonal MF algorithm, BSNMF (Bi-directional Sparse Non-negative Matrix Factorization), that applies bi-directional sparseness constraints superimposed on non-negative constraints, comprising a few dominantly co-expressed genes and samples together. Non-orthogonal MFs tended to show better clustering-quality and prediction-accuracy indices than orthogonal MFs as well as a traditional method, K-means. Moreover, BSNMF showed improved performance in these measurements. Non-orthogonal MFs including BSNMF showed also good performance in the functional enrichment test using Gene Ontology terms and biological pathways. CONCLUSIONS: In conclusion, the clustering performance of orthogonal and non-orthogonal MFs was appropriately evaluated for clustering microarray data by comprehensive measurements. This study showed that non-orthogonal MFs have better performance than orthogonal MFs and K-means for clustering microarray data.