Amikacin Liposome Inhalation Suspension in the Real-World Management of Refractory Mycobacterium avium Complex Pulmonary Disease.

The increasing prevalence of Mycobacterium avium complex (MAC) pulmonary disease poses a significant therapeutic challenge, particularly due to the limited efficacy and systemic toxicity associated with conventional guideline-based therapy. Amikacin liposome inhalation suspension (ALIS) has been developed, yet its real-world application remains underreported. This retrospective analysis, conducted from March 2021 to February 2024, examined ALIS's clinical use in patients aged 20 years or older with refractory MAC pulmonary disease at our institution. The primary objective of this study is to describe the patient characteristics and clinical trajectories associated with the initiation of ALIS therapy in real-world settings for individuals diagnosed with MAC pulmonary disease. Of 11 patients initiated on ALIS, one was excluded due to financial constraints impacting continuation. The analysis proceeded with the remaining 10 subjects. The mean age of participants was 70.2 years, with a predominance of female patients (n = 7, 70%) and a higher incidence of M. avium infections (n = 6, 60%). Forty percent of the cohort (n = 4) had a history of ethambutol-induced optic neuritis leading to the cessation of the drug. The average interval from the initiation of guideline-based therapy to the start of ALIS was 8.5 ± 6.9 years (mean ± standard deviation). The majority (80%) presented with positive Gaffky scores at ALIS initiation, and a significant proportion exhibited resistance to clarithromycin and ethambutol. Comorbid conditions, including diabetes and previous cancer, were noted. The study also observed elevated anti-MAC antibody levels. Treatment duration varied, with fatigue leading to discontinuation in two cases. Treatment-emergent adverse events were documented in individual patients, each presenting with grade 1 severity: hemoptysis (n = 1, 10%), elevated creatinine levels (n = 1, 10%), and dysphonia (n = 2, 20%) were observed, respectively. Correlation analysis revealed a significant inverse relationship between body mass index (BMI) and ALIS discontinuation due to fatigue, and a positive correlation between Gaffky scores and C-reactive protein (CRP) levels. These results underscore the potential benefits and limitations of ALIS, suggesting that timely intervention and comprehensive healthcare support are crucial for optimal outcomes in the treatment of advanced MAC pulmonary disease.

Acute Exacerbation of Idiopathic Pulmonary Fibrosis With Concurrent Cardiac Amyloidosis: A Technetium Pyrophosphate Study.

Amyloidosis presents a diagnostic challenge, particularly when concomitant with severe conditions like acute exacerbations of idiopathic pulmonary fibrosis (IPF). In this report, we detail the case of a 73-year-old patient with acute exacerbation of IPF and simultaneous emergence of cardiac amyloidosis. The patient's clinical journey began with persistent exertional dyspnea, progressing to hypoxemia on admission. Chest CT scans showed extensive ground-glass opacities, consolidations, and pre-existing honeycombing-like cysts and reticular shadows, accompanied by a right-sided pleural effusion. The therapeutic strategy for acute exacerbation of IPF encompassed methylprednisolone pulse therapy, tacrolimus, and nintedanib, augmented with intravenous immunoglobulin and recombinant thrombomodulin. Concurrently, heart failure with preserved ejection fraction was managed with a pharmacological trio: empagliflozin, diuretics, and eplerenone. A hypertrophied heart and low limb voltage prompted an investigation for cardiac amyloidosis, which 99mTechnetium pyrophosphate (99mTc-PYP) scintigraphy confirmed, yielding a probable diagnosis. Following steroid tapering, the patient was discharged home. This case prompted an investigation into the potential role of amyloidosis in pulmonary pathology. Our retrospective review of 10 patients, including four with cardiac amyloidosis, who underwent 99mTc-PYP scintigraphy, revealed a nonsignificant yet notable trend of increased pulmonary accumulation in cardiac amyloidosis cases (median (interquartile range): 5.4×104 (5.3-13.1×104) vs. 3.6×104 (2.4-5.1×104), p=0.0667). Notably, the pulmonary counts in this patient exceeded the negative cohort's mean values, hinting at a possible contribution of amyloid deposition to pulmonary pathology. This study, pioneering in evaluating lung field accumulation of 99mTc-PYP in cardiac amyloidosis, may provide novel insights into the influence of amyloidosis on pulmonary conditions.

Relapsing eosinophilic pneumonia in a patient with recurrent breast cancer receiving abemaciclib plus endocrine therapy.

This report presents the case of a 42-year-old Japanese woman with recurrent hormone receptor-positive breast cancer who developed eosinophilic pneumonia (EP) during treatment with abemaciclib combined with endocrine therapy. Seven years after a radical surgery and definite diagnosis of Stage I breast cancer, her cancer recurred with metastases to multiple organs. Initially treated with abemaciclib plus letrozole and goserelin for 3 months, she developed EP, which improved after the discontinuation of anti-cancer treatment and the administration of prednisolone. However, EP occurred again upon the reintroduction of endocrine therapy (i.e., letrozole and goserelin). It improved gradually with the suspension of endocrine therapy and the re-administration of prednisolone. This case underscores the need for further research into the prevention and management of EP in patients receiving abemaciclib with endocrine therapy for advanced breast cancer.

A Case of Pneumocystis Pneumonia Developed During Rheumatoid Arthritis Treatment With Methotrexate and Golimumab.

Here, we report a case of an 87-year-old female patient with rheumatoid arthritis (RA) treated with methotrexate (MTX) and golimumab who developed severe pneumocystis pneumonia (PCP), also known as Pneumocystis jirovecii pneumonia. The patient presented with chief complaints of dyspnea on exertion, dry cough, and fatigue. A high-resolution chest CT scan revealed diffuse, unevenly distributed ground-glass opacities throughout both lungs. The patient was clinically diagnosed with PCP based on the clinical settings, imaging, and a high level of serum ß-D-glucan. While the patient required high-flow oxygen therapy, low-dose trimethoprim/sulfamethoxazole and corticosteroid therapy improved her condition, and the patient was discharged on day 25. Although to our knowledge no case report has been published regarding PCP in patients with RA treated with golimumab, this case emphasizes the importance of attention to opportunistic infections in elderly patients receiving immunosuppressive therapy. MTX use alongside tumor necrosis factor inhibitors like golimumab may increase the risk of serious infections such as PCP. The case underscores the necessity of prophylactic measures and early intervention for PCP, highlighting the delicate balance between immunosuppression benefits and infection risks in RA management.

Effective treatment of inhaled corticosteroid and bronchodilator for "lymphocytic interstitial pneumonia" in primary Sjögren's syndrome.

We present a case of an 86-year-old woman who visited our hospital with a one-year history of exertional dyspnea (modified medical research council dyspnea scale; mMRC grade 2). Despite the absence of any smoking or dust exposure history, multiple cystic lesions were apparent in both lungs on her CT scan. We suspected Sjögren's syndrome-associated lymphocytic interstitial pneumonia (LIP) due to her additional symptoms of dry mouth and eyes. Her respiratory function test showed a restrictive disorder with a forced vital capacity (FVC) of 1.23 L (70.3 % predicted), forced expiratory volume in 1 s (FEV1) of 0.88 L, and FEV1/FVC of 71.5 %. The flow-volume curve showed a downward convex, suggesting peripheral airway obstruction. We initiated a daily inhalation treatment regimen comprising vilanterol 25 µg and fluticasone furoate 200 µg. One month later, at the follow-up visit, the clinical diagnosis of Sjögren's syndrome with LIP was made by positive SS-A and SS-B antibodies in the initial blood work, a Saxon test that confirmed decreased salivary secretion, and a confirmed diagnosis of dry eyes by her ophthalmologist. We noted improvement in FVC of 1.45 L (+17.8 %) and FEV1 to 0.99 L (+12.5 %) in the subsequent respiratory function test, along with alleviation of her symptoms. The present case represents the first report of LIP treated exclusively with inhaled corticosteroids and bronchodilators, highlighting a potential therapeutic approach, particularly for elderly patients vulnerable to immunosuppressive therapies.

A Teaching Case: Persistent COVID-19 Pneumonia Resembling Cryptogenic Organizing Pneumonia in a Patient With Remitted Lymphoma.

We report a case of a female patient in her 50s, previously diagnosed with follicular lymphoma (now in complete remission), who was admitted to our hospital due to antibiotic-resistant pneumonia lasting a month. The patient had contracted coronavirus disease 2019 (COVID-19) pneumonia a year earlier and exhibited persistent hypogammaglobulinemia. Chest CT scans revealed wondering ground-glass opacities and consolidations initially suggestive of cryptogenic organizing pneumonia (COP). Despite repeatedly negative nasopharyngeal SARS-CoV-2 tests, the virus was detected in the bronchoalveolar lavage fluid (BALF) using the BioFire FilmArray Respiratory Panel 2.1. She was subsequently diagnosed with COVID-19 pneumonia and responded well to treatment with remdesivir (RDV) and intravenous immunoglobulin. The SARS-CoV-2 variant in the BALF was suspected as the Omicron variant (XBB.1.16), prevalent in the area at the admission, indicating a re-infection rather than a recurrence. This case underscores the protracted nature of COVID-19 pneumonia in immunocompromised patients and the risks of false negatives in nasopharyngeal SARS-CoV-2 tests. Direct SARS-CoV-2 measurement from BALF can be crucial in such cases. A COP diagnosis based solely on imaging and administering corticosteroids without antiviral treatment might exacerbate the situation by reactivating SARS-CoV-2. Given the current pandemic, clinicians should be aware of the potential for persistent or recurrent COVID-19, particularly in immunocompromised patients.

Clinical features of relapsed connective tissue disease-associated organizing pneumonia.

BACKGROUND: Organizing pneumonia (OP) is recognized as a nonspecific lung injury response characterized histopathologically by the presence of intra-alveolar buds of granulation tissue. Most OP patients show excellent responses to corticosteroids, but relapse is frequently seen when corticosteroids are tapered or discontinued. Although several factors associated with relapse have been reported in cryptogenic OP (COP), the clinical features and risk factors associated with relapse in connective tissue disease-associated OP (CTD-OP) have yet to be fully understood. METHODS: We retrospectively reviewed data on 47 CTD-OP patients. We investigated the frequency of relapse and compared the clinical data between CTD-OP with and without relapse to clarify the risk factors for relapse. RESULTS: Eleven (23.4%) CTD-OP patients had relapses of OP during the study. In the multivariate analysis, no CTD treatment at OP diagnosis [O.R. 11.920, p = 0.012] and partial remission after steroid treatment [O.R. 35.944, p = 0.045] were independent risk factors for relapse. Among rheumatoid arthritis-associated OP (RA-OP) patients, partial remission after steroid treatment [O.R. 16.151, p = 0.047] and age at OP diagnosis [O.R. 0.899, p = 0.045] were independent risk factors for relapse. Most of the relapsed OP patients who were on no medication at OP diagnosis later developed CTD. CONCLUSION: CTD-OP patients with residual disease on HRCT after treatment and who had OP diagnosis preceding CTD diagnosis were more likely to have an OP relapse. During the clinical course of relapsed OP patients, it is necessary to pay attention to the onset of CTD.

Acute Pneumonitis Associated With the Inhalation of Pyrethroid-Based Domestic Insecticides.

We report a 72-year-old female who presented to our hospital with a worsening cough and dyspnea that had emerged a week earlier following the accidental inhalation of a significant quantity of spray-type imiprothrin (a synthetic pyrethroid)-based insecticide in her bathroom. She exhibited acute respiratory failure necessitating 4 L/minute of nasal oxygen at maximum. Chest CT images showed diffuse centrilobular ground-glass opacities with mosaic attenuation and consolidation areas in the lower lobes of both lungs. The patient was diagnosed with acute pneumonitis due to insecticide inhalation, and her symptoms improved following methylprednisolone pulse and alpha-tocopherol therapy. Generally, the accidental inhalation of aerosolized pyrethroids does not induce significant respiratory symptoms, and case reports on pulmonary toxicity related to pyrethroid inhalation are scarce. This case report underscores the need to include inhaled pyrethroid insecticides in the differential diagnosis of patients with acute pneumonitis and suggests that methylprednisolone and alpha-tocopherol therapy can be beneficial for treating this condition.

Acute exacerbation in antineutrophil cytoplasmic antibody-associated interstitial lung disease: Clinical features and risk factors.

BACKGROUND: Acute exacerbation (AE) is a life-threatening clinical event that occurs during the clinical course of idiopathic pulmonary fibrosis (IPF). Several studies have reported that AE also occurs in interstitial lung disease (ILD) other than IPF. However, the incidence, clinical features, risk factors for AE, and major causes of death in antineutrophil cytoplasmic antibody (ANCA)-associated ILD (ANCA-ILD) patients have not been well established. METHODS: We retrospectively reviewed the data of 54 ANCA-ILD patients and 304 IPF patients. We investigated the frequency of AE, post-AE prognoses, risk factors for AE, and major causes of death in ANCA-ILD patients. We also compared the data of ANCA-ILD with that of IPF. RESULTS: Fourteen (25.9%) ANCA-ILD patients and 84 (27.6%) IPF patients developed AE. The median survival times (MSTs) after AE in ANCA-ILD and IPF patients were 35.5 and 60 days, respectively (p = 0.588, log-rank test). In a multivariate analysis, the percentage of predicted forced vital capacity (%FVC) [O.R. 0.750 (95% CI 0.570, 0.986), p < 0.01] and serum C-reactive protein (CRP) [O.R. 2.202 (95% CI 1.037, 4.674), p < 0.01] were independent risk factors for AE. AE was the most frequent cause of death in ANCA-ILD and IPF patients. CONCLUSION: ANCA-ILD patients could develop AE, and the frequency of AE in ANCA-ILD is similar to that in IPF. AE is the most frequent cause of death in ANCA-ILD patients. A low %FVC and a high serum CRP level were independent predictive factors for AE in ANCA-ILD. The prognosis after AE in ANCA-ILD was poor, as it was in IPF.

Clinical features of acute exacerbation in rheumatoid arthritis-associated interstitial lung disease: Comparison with idiopathic pulmonary fibrosis.

BACKGROUND: Several studies have reported that acute exacerbation (AE), which occurs during the clinical course of idiopathic pulmonary fibrosis (IPF), also occurs in rheumatoid arthritis-associated interstitial lung disease (RA-ILD). However, the incidence, clinical features, and risk factors for AE, a major cause of death of RA-ILD patients, and the differences in clinical aspects of AE between RA-ILD and IPF have yet to be fully understood. METHODS: We retrospectively reviewed data on 149 RA-ILD patients and 305 IPF patients. We investigated the frequency of AE and compared the clinical data between RA-ILD with and without AE to clarify the risk factor for AE. We also compared the post-AE prognosis and cause of death between RA-ILD and IPF patients. RESULTS: Twenty-seven (18.1%) RA-ILD patients and 84 (27.5%) IPF patients developed AE. The median survival time (MST) after AE of RA-ILD and IPF was 277 days and 60 days, respectively (log rank, p = 0.038). In a multivariate analysis, hypoalbuminemia [odds ratio (O.R.) 0.090 (95%CI 0.011-0.733), p = 0.012] and % carbon monoxide diffusion capacity (%DLCO) [O.R. 0.810 (95%CI 0.814-0.964), p < 0.01] were independent risk factors for AE. AE was the most frequent cause of death of RA-ILD and IPF. CONCLUSION: RA-ILD patients could develop AE, and AE was not uncommon in RA-ILD or IPF. %DLCO and hypoalbuminemia were predictive factors of AE in RA-ILD. The prognosis after AE of RA-ILD was significantly better than that of IPF. The most frequent cause of death in RA-ILD and IPF was AE.

Combination immunotherapy of nivolumab plus ipilimumab in a lung cancer patient with Werner syndrome; a case report.

Werner syndrome (WS) is a rare progressive disorder that is characterized by premature aging of all organs. Malignancy is a frequent complication of WS, however, lung cancer patients with WS are much rare. In patients with WS, the treatment for malignancy is often limited due to other complications of severe skin ulcer, diabetes mellitus and cardiovascular disease. Currently, immune-checkpoint inhibitors (ICIs) are standard therapy for several cancer patients and the combination of nivolumab plus ipilimumab has also been approved for the treatment of non-small cell lung cancer (NSCLC). Recent studies have also reported that serious immune-related adverse events (irAEs) induced by ICIs may correlate with elderly or more vulnerable patients. However, the efficacy and safety of ICIs in NSCLC patients with WS remain unclear. To the best of our knowledge, this is the first case describing a NSCLC patient with WS receiving the combination immunotherapy of nivolumab and ipilimumab. Our case showed objective response to ICIs, however, several immune-related adverse events (irAEs) including hypothyroidism, adrenal insufficiency, hard rash and interstitial lung disease occurred, thus resulted in early treatment discontinuation. Our case suggests that immunotherapy for NSCLC patients with WS could be effective, but physicians may be aware of the possibility of multiple irAEs undergoing immunotherapy for NSCLC patients with WS.

Pleural empyema with gas formation caused by mixed infection of Edwardsiella tarda with Streptococcus constellatus.

Edwardsiella tarda is an anaerobic, gram-negative rod bacterium associated with freshwater and marine life. Human E. tarda infections are rare, and most infections in humans cause gastroenteritis. Extraintestinal infections of E. tarda such as pleural empyema are particularly rare. A 72-year-old man was admitted with cough and purulent sputum. His medical history included periodontal disease and gastric cancer for which he had undergone total gastrectomy. Chest computed tomography showed left pleural effusion with foci of gas, and both E. tarda and Streptococcus constellatus were cultured from the pleural effusion. Thus, he was diagnosed with gas-forming empyema. He was successfully treated with therapeutic thoracentesis and antibiotics. Our case suggests that a dietary habit of raw fish, undernutrition, gastrectomy and oral infection may be predisposing factors for empyema caused by E. tarda.

The Evaluation of the Sputum Antigen Kit in the Diagnosis of Pneumococcal Pneumonia.

Objective A previously developed sputum antigen detection kit for Streptococcus pneumoniae enabled the early diagnosis of pneumococcal pneumonia using sputum samples. We conducted a prospective study to compare the sensitivity of the sputum and urinary antigen kits. Methods Pneumonia patients who were treated from April 2014 to September 2015 were recruited for the present study. Patients with pneumococcal pneumonia who could not participate in the prospective arm of the study were analyzed in the retrospective arm. Results Nine of the 69 participants in the prospective study had pneumococcal pneumonia. The sputum antigen kit results correlated well with the sputum culture results. The sensitivity of the sputum antigen kit was 88.9% (8/9), which was higher than that of the urinary antigen kit (5/9; 55.6%). When patients from the retrospective arm of the study were included, the sensitivity of the sputum culture was 93.5% (29/31), which was significantly higher than that of the urinary antigen kit (19/31; 60.6%). False positives were obtained using the sputum antigen kit in four cases. Three of the four false positives were suspected to have resulted from the administration of antibiotics prior to the use of the kit; the remaining case likely occurred due to a false reaction to S. milleri-induced pyothorax. Conclusion Collectively, our findings suggest that the sputum antigen kit has a higher sensitivity for detecting S. pneumoniae than the urinary antigen kit. However, the prior administration of antibiotics can render the sputum culture results negative or lead to a false-positive result.

Inhaled granulocyte/macrophage-colony stimulating factor as therapy for pulmonary alveolar proteinosis.

RATIONALE: Inhaled granulocyte/macrophage-colony stimulating factor (GM-CSF) is a promising therapy for pulmonary alveolar proteinosis (PAP) but has not been adequately studied. OBJECTIVES: To evaluate safety and efficacy of inhaled GM-CSF in patients with unremitting or progressive PAP. METHODS: We conducted a national, multicenter, self-controlled, phase II trial at nine pulmonary centers throughout Japan. Patients who had lung biopsy or cytology findings diagnostic of PAP, an elevated serum GM-CSF antibody level, and a Pa(O(2)) of less than 75 mm Hg entered a 12-week observation period. Those who improved (i.e., alveolar-arterial oxygen difference [A-aDO(2)] decreased by 10 mm Hg) during observation were excluded. The rest entered sequential periods of high-dose therapy (250 microg Days 1-8, none Days 9-14; x six cycles; 12 wk); low-dose therapy (125 microg Days 1-4, none Days 5-14; x six cycles; 12 wk), and follow-up (52 wk). MEASUREMENTS AND MAIN RESULTS: Fifty patients with PAP were enrolled in the study. During observation, nine improved and two withdrew; all of these were excluded. Of 35 patients completing the high- and low-dose therapy, 24 improved, resulting in an overall response rate of 62% (24/39; intention-to-treat analysis) and reduction in A-aDO(2) of 12.3 mm Hg (95% confidence interval, 8.4-16.2; n = 35, P < 0.001). No serious adverse events occurred, and serum GM-CSF autoantibody levels were unchanged. A treatment-emergent correlation occurred between A-aDO(2) and diffusing capacity of the lung, and high-resolution CT revealed improvement of ground-glass opacity. Twenty-nine of 35 patients remained stable without further therapy for 1 year. CONCLUSIONS: Inhaled GM-CSF therapy is safe, effective, and provides a sustained therapeutic effect in autoimmune PAP. Clinical trial registered with www.controlled-trials.com/isrctn (ISRCTN18931678), www.jmacct.med.or.jp/english (JMA-IIA00013).

Molecular analysis of a novel hereditary C3 deficiency with systemic lupus erythematosus.

A case of inherited homozygous complement C3 deficiency (C3D) in a patient with systemic lupus erythematosus (SLE) and the molecular basis for this deficiency are reported. A 22-year-old Japanese male was diagnosed as having SLE and his medical history revealed recurrent tonsillitis and pneumonia. He was diagnosed as having C3D because of undetectable serum C3 level. His parents were consanguineous. Sequence analysis of C3D cDNA revealed a homozygous deletion of exon 39 (84bp). A single base substitution (AG to GG) in the 3'-splice acceptor site of intron 38 was identified by sequencing the genomic DNA. Expression of C3Delta(ex39) cDNA, the C3cDNA lacking exon 39, in COS-7 cells revealed that C3Delta(ex39) was retained in endoplasmic reticulum-Golgi intermediate compartment because of defective secretion. These data indicate that a novel AG-->GG 3'-splice acceptor site mutation in intron 38 caused aberrant splicing of exon 39, resulting in defective secretion of C3.

Infliximab induces potent anti-inflammatory responses by outside-to-inside signals through transmembrane TNF-alpha.

BACKGROUND AND AIMS: Both infliximab (chimeric anti-tumor necrosis factor [TNF]-alpha antibody) and etanercept (p75 TNF-alpha receptor/immunoglobulin G fusion protein) are effective against rheumatoid arthritis, but only infliximab induces clinical remission in Crohn's disease. To clarify this difference in clinical efficacy, we investigated reverse signaling through transmembrane TNF-alpha (mTNF) by these 2 anti-TNF agents. METHODS: We stably transfected wild-type and cytoplasmic serine-replaced mutant forms of mTNF in human Jurkat T cells. Cells were stimulated with infliximab and etanercept and then analyzed for E-selectin expression, reactive oxygen species accumulation, apoptosis, and cell cycle distribution by flow cytometry. Interleukin-10 and interferon-gamma were measured by enzyme-linked immunosorbent assay. Phospho-c-Jun NH2-terminal kinase, Bax, Bak, p21(WAF1/CIP1), caspase-8, and caspase-3 were examined by immunoblotting. RESULTS: Both anti-TNF agents induced E-selectin expression, but only infliximab induced interleukin-10 production, apoptosis, and G0/G1 cell cycle arrest. Apoptosis and cell cycle arrest were abolished by substitution of all 3 cytoplasmic serine residues of mTNF by alanine residues. Infliximab induced accumulation of reactive oxygen species and up-regulation of Bax, Bak, and p21(WAF1/CIP1) proteins, suggesting the involvement of p53 activation. Moreover, phosphorylation of c-Jun NH2-terminal kinase was necessary for infliximab-induced apoptosis and cell cycle arrest. CONCLUSIONS: We revealed the mTNF motifs and the downstream intracellular molecular events essential for reverse signaling through mTNF. The biologic effects of mTNF elicited by infliximab should be important action mechanisms of this potent anti-inflammatory agent in addition to the neutralization of soluble TNF-alpha. These observations will provide insight into the novel role of mTNF in inflammation.

Association of a four-amino acid residue insertion polymorphism of the HS1 gene with systemic lupus erythematosus: molecular and functional analysis.

OBJECTIVE: To investigate whether polymorphism(s) or mutation(s) in the hematopoietic cell-specific Lyn substrate 1 (HS1) gene are involved in the pathogenesis of systemic lupus erythematosus (SLE). METHODS: The entire coding region of the HS1 gene was analyzed by reverse transcriptase-polymerase chain reaction/single-strand conformational polymorphism analysis. HS1-transfected WEHI-231 cells or B lymphocytes from patients with SLE were studied for apoptosis, activation, and proliferation by flow cytometric analysis and MTT assay. RESULTS: We identified a glutamic acid-proline-glutamic acid-proline insertion between codons 366 and 367 (EPEP366-367ins) and 2 amino acid substitutions (A235T and E361K). The genotype frequency among individuals homozygous for the EPEP+ allele was 0.184 in 201 patients with SLE but only 0.098 in 184 healthy individuals (P = 0.016). The allele frequency of EPEP366-367ins was 0.408 in patients with SLE; this frequency was significantly higher than that in healthy controls (0.312) (P = 0.006). WEHI-231 cells transfected with EPEP+ HS1 were 100-fold more sensitive to B cell receptor (BCR)-mediated apoptosis than were those transfected with HS1 without EPEP. B lymphocytes from SLE patients with the EPEP+ allele were significantly more apoptotic without BCR stimulation and less activated after BCR stimulation than were those from SLE patients without the EPEP allele. CONCLUSION: These results suggest that HS1 with the EPEP insertion polymorphism transmits accelerated signals from BCR and is involved in the pathogenesis of SLE.