Citations

Abstract Background Sulfhemoglobinemia is a rare but potentially life-threatening dyshemoglobinemia resulting from the irreversible incorporation of sulfur into the heme moiety, producing hemoglobin species incapable of oxygen transport. Its clinical presentation often mimics methemoglobinemia, with cyanosis and oxygen saturation (SpO2) readings discordant from arterial partial pressure of oxygen (PaO2). Phenazopyridine, an over-the-counter urinary analgesic, has been implicated as a rare cause, in 3 previously documented cases. Prompt recognition is essential to avoid inappropriate therapy, particularly methylene blue, which can precipitate hemolysis in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Case Presentation A 71-year-old man with Parkinson’s disease, Crohn’s disease, and chronic anemia presented with unexplained cyanosis and SpO2 readings in the 70-80% range, despite a normal PaO2 of 180 mmHg and absence of respiratory symptoms. He had self-initiated phenazopyridine for dysuria three days prior. CT angiography of the chest and echocardiography with bubble study were unremarkable. Attempts to quantify methemoglobin and carboxyhemoglobin were unsuccessful due to analyzer errors. Laboratory evaluation revealed acute anemia (hemoglobin 5.7 g/dL), indirect hyperbilirubinemia, and low haptoglobin consistent with hemolysis. He was managed supportively with high-flow oxygen, and transfusion of two packed red blood cell units. Although initial G6PD levels were normal, testing during hemolysis can yield false negatives. Given this and the risk of methylene blue-induced oxidative stress, conservative management with ascorbic acid was chosen. The patient’s SpO2 improved gradually, and he was discharged on hospital day three. Send-out tests later confirmed sulfhemoglobinemia (1.1%), elevated cytochrome b5 reductase activity, and normal methemoglobin. Discussion This case underscores the diagnostic and therapeutic challenge of differentiating sulfhemoglobinemia from methemoglobinemia. Both disorders produce functional hypoxia with SpO2-PaO2 dissociation, but sulfhemoglobin cannot revert to hemoglobin and requires erythrocyte turnover for resolution. While methylene blue is the standard therapy for methemoglobinemia, it is ineffective for sulfhemoglobinemia and contraindicated in G6PD deficiency. In our patient, supportive care and transfusion facilitated recovery. Using the Naranjo Adverse Drug Reaction Probability Scale, the causality score was 7, indicating a highly probable relationship between phenazopyridine exposure and sulfhemoglobinemia. A high index of suspicion for G6PD deficiency as well as dyshemoglobinemia with a multidisciplinary collaboration are essential for diagnosis and management of unexplained cyanosis. This abstract is funded by: None

Abstract Introduction Phrenic neuropathies (PN) are an important cause of dyspnea and hypercapnic respiratory failure. A crucial yet often overlooked symptom is dyspnea associated with water immersion activities. This symptom which is frequently documented in patients with PN, carries a serious risk of drowning and should serve as a key clinical clue for underlying diaphragmatic weakness. This report details a case of severe unilateral diaphragmatic paralysis, where immersion dyspnea served as the respiratory harbinger guiding the diagnosis in a competitive athlete. Case Description A 47-year-old male athlete training for an Ironman triathlon, presented with exercise-induced dyspnea, wheezing and orthopnea following a major bike accident involving left sided trauma (rib fractures, pneumothorax, left clavicle/scapula fracture). Notably he reported difficulty swimming or water immersion dyspnea even before the accident. Chest x-ray revealed an elevated right hemidiaphragm. Pulmonary Function Tests (PFTs) showed normal baseline spirometry and diffusing capacity but Maximal Inspiratory Pressure (MIP) was reduced (51 cmH2O), indicating neuromuscular weakness. Cardiopulmonary Exercise Testing (CPET) demonstrated supranormal exercise capacity (Peak VO2 4.13 L/min, 122% predicted, Peak Work Rate 385 W, 170% predicted) with reduced breathing reserve of 2.4%, arguably normal with the other supranormal exercise parameters in a highly conditioned athlete. Electromyography (EMG) and nerve conduction studies revealed an absent right phrenic motor response while diaphragmatic ultrasound confirmed severe right hemidiaphragm atrophy (thickness 0.05 cm; normal >0.15 cm) and a poor thickening ratio (0.5; normal >1.2). Discussion Immersion dyspnea should immediately raise suspicion for phrenic neuropathy (PN) even in otherwise healthy and athletic individuals. In a Mayo Clinic study of 535 PN patients, only 4% (22 of 535) reported dyspnea triggered specifically by water immersion underscoring the rarity of this symptom. For 36% (8 of 22) immersion dyspnea was the first respiratory symptom and in 4.5% (1 of 22) it was the only symptom. Notably 18% (4 of 22) experienced near-drowning incidents. The hydrostatic pressure exerted by water worsens the mechanical disadvantage caused by a paralyzed diaphragm making immersion dyspnea a vital diagnostic warning sign. Because of its rarity but serious risks patients with diaphragmatic paralysis should be advised to avoid immersion activities particularly diving. This abstract is funded by: nnone

Abstract Rationale Treatment of hematologic malignancies has been revolutionized by Chimeric antigen receptor T -cell (CAR-T) therapy. Pulmonary complications are increasingly being reported, however, there are no standardized timelines for pulmonary function test (PFTs) assessment before or after the infusion. We aimed to evaluate changes in lung function (TLC, RV, FEV1, and FEV1/FVC) pre- and post-CAR-T therapy and examine whether these parameters correlate with the development of specific pulmonary complications. Methods We conducted a retrospective chart review of patients above the age of 18 with any malignancy who received CAR-T therapy between June 12, 2018, and December 26, 2023. Pre-CAR-T PFTs were obtained closest to the infusion date, and post-CAR-T PFTs were recorded at the earliest available time following infusion. Pre- and post-CART pulmonary function tests were compared using non-parametric paired tests. In addition, we examined the relationship between baseline PFTs and the subsequent occurrence of pulmonary complications after CAR-T infusion. The Wilcoxon signed-rank test was applied to assess both the magnitude and direction of change while Sign test was used to evaluate only the direction to confirm the consistency of results. These tests were chosen due to small sample size and non-normal distribution of data. Results Among the 68 patients in our cohort, paired pre- and post- CAR-T measurements of pulmonary function were available for 18 patients. FEV1 declined significantly post-infusion (2.70 ± 0.81 L vs 2.28 ± 0.74 L; Z= -2.55, p = 0.011), the FEV1/FVC ratio remained stable (77.8 ± 8.0 vs 80.9 ± 12.2, p = 0.53). Mean TLC and RV remained stable (TLC 5.70 ± 1.18 L vs 4.66 ± 1.02 L, p = 0.17 and 2.13 ± 0.62 L vs 2.00 ± 0.70 L, p = 0.58). There was no significant correlation between the baseline lung function and the development of pulmonary complications. Conclusion Only the pattern of FEV1 decline following CAR-T therapy infusion demonstrates a significant decline, whereas other PFTs, although reduced, did not show significance. While these findings may suggest a restrictive ventilatory pattern, additional data on lung volumes are required to accurately characterize the underlying type of pulmonary function impairment. Although limited by small sample size and non-uniform timing of PFT assessments, this highlights the need for a routine pre-CAR-T pulmonary function evaluation to inform patient selection and baseline risk stratification. This abstract is funded by: None

Abstract Background With recent advances in oncology, tyrosine kinase inhibitors like imatinib play a significant role in gastrointestinal stromal tumor (GIST) treatment but can cause rare pulmonary complications. When new respiratory symptoms arise after starting these agents, differentiating drug toxicity from other lung diseases is important for timely management. Case Presentation A 72-year-old man with GIST, recently started on imatinib, presented with acute dyspnea and hypoxia. His medical history included chronic obstructive pulmonary disease and a 40-pack-year smoking history. Chest CT revealed new bilateral interstitial infiltrates absent on imaging two months ago, prior to imatinib initiation. The differential diagnosis included imatinib-induced pneumonitis versus atypical infection. Bronchoscopy showed yellowish nodular mucosa throughout the trachea and bronchi, mucus plugging, and airway narrowing in the left lower lobe. Endobronchial biopsies demonstrated amyloid deposits consistent with tracheobronchial amyloidosis. The bronchoalveolar lavage was negative for infection and, therefore, corticosteroid therapy was initiated, resulting in clinical and radiographic improvement. The findings supported a diagnosis of imatinib-induced pneumonitis coexisting with tracheobronchial amyloidosis. Discussion This case highlights the diagnostic challenges when drug-induced pneumonitis occurs along with structural airway abnormalities. Tracheobronchial amyloidosis, although rare, can cause airway obstruction and coexist with inflammatory lung conditions. The temporal association with imatinib, exclusion of infection, and steroid responsiveness indicate imatinib-induced pneumonitis as the primary cause of the acute symptoms, with concurrent amyloid deposition contributing to airway pathology. Conclusion In patients developing new pulmonary symptoms after starting tyrosine kinase inhibitors, drug-induced pneumonitis should be strongly suspected. The coexistence of airway diseases such as tracheobronchial amyloidosis can complicate diagnosis and management, highlighting the need for thorough evaluation including bronchoscopy and tissue biopsy to guide treatment. This abstract is funded by: None

Abstract Introduction Drug-induced pneumonitis is an important mimic of disseminated infection in immunocompromised hosts. Lenalidomide, an immunomodulatory agent widely used in multiple myeloma, has been associated with organizing and eosinophilic pneumonitis, and occasionally sarcoid-like granulomatous inflammation. The coexistence of acute fibrinous injury and granulomatous inflammation is exceptionally rare. We present a case of lenalidomide-associated acute fibrinous and granulomatous pneumonitis presenting with a miliary pattern following autologous stem cell transplant. Case Presentation A 44-year-old woman with kappa light-chain multiple myeloma, chronic kidney disease stage V, presented with 10 days of fever (to 105 °F), dry cough, hemoptysis, dyspnea and hypoxia requiring high flow oxygen. She had been on maintenance therapy with lenalidomide, daratumumab, and weekly dexamethasone after undergoing an autologous stem cell transplant for multiple myeloma, last administered one week before symptom onset.. CT chest (Figure 1-1) showed innumerable randomly distributed micronodules with ground-glass opacities and septal thickening, suggesting disseminated infection. Laboratory results revealed eosinophilia (950/µL), neutropenia, and profound hypogammaglobulinemia. Empiric piperacillin-tazobactam, doxycycline, and fluconazole were started for possible bacterial and/or fungal infection (history of positive Coccidioides IgM). Two bronchoscopies demonstrated multifocal hypervascular airway lesions. BAL differential showed 15 % eosinophils and > 30 % lymphocytes; cultures, Fungitell, and comprehensive testing for bacterial, fungal, mycobacterial, viral, and parasitic pathogens were negative. Cryobiopsy revealed acute fibrinous and granulomatous pneumonitis with negative GMS and acid-fast stains. Following withdrawal of lenalidomide and daratumumab, the patient’s symptoms and CT findings improved without further antimicrobial therapy within the same hospitalization (Figure 1-2). She received an 8-week prednisone taper with inhaled pentamidine prophylaxis. Follow-up CT showed complete clinical and radiographic resolution (Figure 1-3), confirming a grade 3 drug-induced pneumonitis. A bronchoscopy will be repeated to assess the endobronchial vascular lesions. Discussion Lenalidomide related lung injury typically manifests as organizing or eosinophilic pneumonitis. The presence of both fibrinous and granulomatous inflammation suggests a mixed hypersensitivity and immune-complex reaction possibly potentiated by immune reconstitution after autologous transplant. The miliary pattern and BAL eosinophilia closely mimic disseminated fungal or mycobacterial infection. A Naranjo Adverse Drug Reaction Probability Scale score of 7 supported a highly probable causal relationship. Awareness of this pattern is essential, as prompt drug cessation and corticosteroid therapy are curative and prevent progression to fibrotic lung injury. This abstract is funded by: None

Abstract RATIONALE There are limited studies evaluating the association between chimeric antigen receptor T-cell (CAR-T) therapy and interstitial lung abnormalities (ILA). Our study aims to investigate this potential relationship to better understand pulmonary complications following CAR-T therapy. Methods We conducted a retrospective chart review of patients aged 18 or older with any malignancy who received CAR-T therapy between June 12, 2018, and December 26, 2023. Chest imaging, including PET or CT scans, was reviewed for each patient; the closest scan before CAR-T therapy and the most recent scan afterward. We identified ILA based on findings that included ground-glass opacities, reticular abnormalities, traction bronchiectasis, honeycombing, or non-emphysematous cysts involving more than 5% of lung zones. We excluded dependent atelectasis, paraspinal fibrosis, aspiration-related changes, mild focal or unilateral abnormalities, and smoking-related centrilobular nodularity without other findings. Results A total of 66 patients had adequate imaging data both before and after CAR-T infusion. Before therapy, 17 patients (25.8%) demonstrated ILA, while 49 (74.2%) did not. Following CAR-T therapy, the overall prevalence of ILA increased to 31 patients (47.0%). Among those who did not have ILA before CAR-T, 16 of 49 (32.7%) developed new ILA following therapy. Conversely, among those with pre-existing ILA, 14 of 17 (82.4%) showed persistent or progressive ILA post-CAR-T. This distribution demonstrated a statistically significant association between pre- and post-CAR-T ILA status (χ² = 10.8, p = 0.001), indicating that pre-CAR-T ILA status strongly predicted post-CAR-T ILA persistence or worsening. When evaluating post-CAR-T ILA in relation to clinical outcomes, among those with pre-CAR-T ILA, 52.9% (n = 9) were deceased at follow-up, compared to 55.1% (n = 27) among patients without ILA. The difference in mortality between the groups was not statistically significant (χ² = 2.34, p = 0.31). 19 of 31 patients (61.3%) with post-CAR-T ILA were deceased at last follow-up, compared with 17 of 37 (45.9%) in those without ILA. Although mortality was numerically higher among patients with post-CAR-T ILA, this difference did not reach statistical significance (χ² = 1.04, p = 0.308). Conclusion Our study demonstrates a statistically significant association between pre- and post-CAR-T interstitial lung abnormalities, suggesting that CAR-T therapy may contribute to the progression or development of ILAs. These findings highlight the need for closer pulmonary monitoring during CAR-T treatment. This abstract is funded by: None

Abstract Rationale Inflammatory bowel disease (IBD) is increasingly recognized as a systemic disorder, with extraintestinal manifestations (EIMs) involving multiple organ systems. Pulmonary involvement, particularly interstitial lung disease (ILD), remains an underrecognized manifestation of IBD. Its prevalence, clinical characteristics, and risk factors in IBD remain poorly defined. Methods We conducted a retrospective study of adults (≥18 years) with IBD who had at least one encounter in our health system between January 1, 2013 and December 31, 2023. IBD, and ILD cases were identified using ICD-9/ICD-10 codes, with ILD diagnoses confirmed by thoracic radiologists. Demographic, clinical, pulmonary, smoking, medication, and surgical data were abstracted. Associations between patient characteristics and ILD were evaluated using both a cohort design and a matched case-control design (1:3 ratio). Mortality was assessed using a Cox proportional hazards model with ILD as a time-dependent covariate. Results Among 875 patients with IBD, 109 (12%) had ILD. Radiographic patterns included nonspecific interstitial pneumonia (NSIP, 27%), indeterminate (26%), definite/probable UIP (24%), hypersensitivity pneumonitis (15%), and organizing pneumonia (8%). Pulmonary function testing demonstrated predominantly restrictive physiology and impaired diffusion capacity. In multivariable analysis, higher BMI (OR 1.04), bronchiectasis (OR 2.65), ex-smoking (OR 2.15), and use of adalimumab (OR 2.04) or infliximab (OR 2.14) were independently associated with ILD. The matched case-control design confirmed these findings and also identified older age (OR 1.04) as a significant factor. ILD was strongly associated with mortality (HR, 3.78; 95% CI, 2.50-5.72; p < 0.001). Conclusions ILD occurs in a meaningful subset of patients with IBD and is associated with older age, higher BMI, prior smoking, bronchiectasis, and TNF inhibitor use. ILD confers a markedly increased risk of death, highlighting the importance of early recognition and close monitoring in this population. This abstract is funded by: None

Abstract Rationale Patients with idiopathic pulmonary fibrosis (IPF) living in disadvantaged neighborhoods have worse composite outcomes and pulmonary function. Although the current FDA approved drugs reduce lung function decline and may improve mortality for this progressive and fatal disease, equitable access to therapy remains a challenge, which may be contributing to low antifibrotic uptake. Existing understanding of social determinants of health in IPF is derived from local registries and special subpopulations, such as Veterans. The aim of our study is to investigate the association between neighborhood-level deprivation indicators and both the distribution of patients with IPF and outcomes in a large national database. Methods We performed a retrospective cohort analysis between October 1st, 2014, and December 31st 2022, using the Optum Labs Data Warehouse, a large de-identified administrative claims database. We used claims data from commercial, Medicare Advantage, and Medicare Fee-for-Service enrollees across the United States. Diagnosis of IPF was defined using ICD-9 and ICD-10 codes. Social deprivation index (SDI), assessed at the zip code tabulation area level, was determined based on 7 demographic characteristics from the 2015-2019 American Community Survey. Patients were grouped in quintiles based on SDI at diagnosis, where higher values reflect greater deprivation. Hazard ratios (HR) were calculated for all-cause mortality as primary and hospitalization as secondary outcome. Results A total of 96,143 patients (mean age 75.1 years ± 6.9 years) were included in the study, 23.5% received antifibrotics. As area deprivation increased, proportion of female, Black, and Hispanic patients increased, whereas, proportion of male, White, and Asian patients decreased. Similarly, antifibrotic use declined slightly, while prescription of steroids and oxygen increased with SDI. Residing in most disadvantaged neighborhoods increased risk of hospitalization (HR, 1.13 [95% CI 1.09 - 1.17] and all-cause mortality (HR, 1.15 [95% CI 1.11 - 1.19]) after adjusting for covariates over median follow-up of 301 days and 680 days, respectively. Conclusion Gender and racial disparities were evident among IPF patients who live in resource-limited areas. Our study shows that greater proportion of female, Black, and Hispanic IPF patients were disproportionately represented in more socioeconomically deprived areas. Furthermore, as area-level disadvantage increased, fewer patients received antifibrotics, while more patients were on steroids and oxygen therapy potentially indicating more advanced disease. Moreover, living in disadvantaged neighborhoods was associated with worse all-cause mortality and hospitalizations. Identifying individuals who live in socioeconomically disadvantaged areas is essential to provide equitable care and improve outcomes for this life-threatening disease. This abstract is funded by: None

Abstract Rationale Pulmonary Fibrosis (PF) is a fibroproliferative disease characterized by increased proliferation, constant extracellular matrix (ECM) deposition, and dysfunctional antioxidant systems. In PF, an emerging initiator is abnormal iron regulation and lipid peroxidation: consequences of iron catalyzed cell death, i.e. ferroptosis (FP). Abnormal iron regulation and lipid peroxidation lead to diminished glutathione (GSH)/glutathione peroxidase 4 (GPX4) antioxidant systems which promote ECM signaling in fibroblasts. Accordingly, inhibiting ferroptosis and/or correcting iron dysregulation via increasing GSH can help with early PF intervention. We hypothesize that enhanced hydrogen sulfide (H2S) signaling through exogenous H2S donors GYY4137 (slow-releasing) and AP39 (mitochondrial-specific), can blunt FP/lipid peroxidation leading to reduced ECM deposition in the context of PF. Methodsand Results Human fibroblasts were isolated from lung tissue of patients with PF and healthy patients (Mayo IRB approved) and were treated with exogenous H2S donors. Prussian blue staining of FFPE lung sections from patients with PF revealed increased ferric iron in alveolar regions. Immunostaining of PF human lung tissue showed lower expression of H2S generating enzyme, CBS, and higher expression of the lipid peroxidation enzyme, ACSL4, compared to non-PF patients. At the cellular level, Western blot was performed in fibroblasts to understand the effect of PF on Fe regulation. PF fibroblasts showed higher expression of transferrin receptor (TfR1) and ferritin, as well as higher expression of ACSL4. The impact of exogenous H2S donors on PF fibroblasts was tested. While H2S donors did not impact TfR1 or ferritin, they did blunt lipid peroxidation as determined using live cell BDP 581/591 C11- fluorescent imaging and ACSL4 protein expression. Furthermore, GYY4137 increased the cysteine transport protein xCT(SLC7A11; part of xC), the H2S synthesis enzyme CBS and GPX4, overall showing an antioxidant effect. This was further substantiated though measuring GSH/GSSG ratios via luminescence assay. In PF fibroblasts, GSH/GSSG levels were low comparatively to normal fibroblasts. However, with exogenous H2S, PF fibroblasts showed increased GSH/GSSG levels indicating a restoration of antioxidant function. Deposition of collagen-1 was higher in PF fibroblasts, and was blunted by GYY4137, which was more potent than the FP inhibitor ferrostatain-1. Conclusion Our data suggests ferroptosis/impaired antioxidant systems are significant factors in PF and that exogeneous H2S can be leveraged to replenish antioxidant systems and blunt FP, thus potentially reducing fibrotic activity. This abstract is funded by: NIH T32 HL 176414 (Ravi), R01 HL160570 (Pabelick, Prakash), R01 HL158532 (Prakash)

Abstract Rationale Lymphangioleiomyomatosis (LAM) is a rare, progressive, cystic lung disease affecting women. Sirolimus has been shown to stabilize lung function in women with LAM, but real-world data on long-term safety and efficacy are limited. Methods The NIH Multicenter Safety and Durability of Sirolimus for LAM (MIDAS, NCT02432560) observational registry was launched in 2015. All adult (≥18 years) women with LAM (treated or untreated) were eligible to enroll at any of the 20 U.S. sites and followed longitudinally with serial assessments of lung function, health-related quality of life, and treatment related adverse event (TRAEs). Baseline cohort characteristics and TRAEs are summarized using descriptive analyses. Marginal structural models (MSMs) with inverse probability of treatment weighting estimated the causal effect of sirolimus on annualized forced expiratory volume in one-second (FEV1) decline, adjusting for age at LAM diagnosis, prior treatment with sirolimus, menopausal status, race, presence of angiomyolipomas, supplemental oxygen use; time-varying covariates included diffusing capacity for carbon monoxide (DLCO) and serum vascular endothelial growth factor-D (VEGF-D) levels. Results Longitudinal data was available in 350 LAM patients, most of whom (246, 70.3%) had sporadic LAM. The median age at the baseline pulmonary function test (PFT) measurement was 46 years (range: 19 - 74) and the median (IQR) number of serial PFTs obtained per patient was 3 (1 - 5). The average follow-up duration per patient was 2.8 years. Over half of the patients (196, 56%) were treated with sirolimus during the MIDAS observation period for a median (IQR) treatment duration of 4.9 (2.4 - 7.5) years. MSM analysis demonstrated that sirolimus treatment was durably effective and reduced FEV₁ decline by 74.36 mL/year (95% CI: 15.87 - 132.85) compared with no treatment (-85.31 mL/year for the untreated group vs. -10.95 mL/year for the treated group, p = 0.01). Sirolimus was generally well tolerated; treatment interruption ≥3 months was observed in 38 (19.4%) of the 196 sirolimus treated patients. Logistic regression analysis showed that higher levels of FEV1 (odds ratio: OR = 3.12 [1.45 - 7.11], p = 0.005), VEGF-D (OR = 1.0007 [1.0004 - 1.001], p < 0.001), and DLCO (OR = 1.023 [1.0053 - 1.0413, p = 0.01]), were associated with treatment interruption. Conclusions In the MIDAS cohort, sirolimus treatment resulted in durable stabilization of lung function with a favorable safety profile over a 5-year period. These real-world data support sirolimus as a chronic suppressive therapy for LAM, demonstrating durable efficacy in slowing lung disease progression and tolerability with long-term use. This abstract is funded by: National Institutes of Health