Healthcare resource utilization of patients with warm autoimmune hemolytic anemia initiating first line therapy of oral corticosteroids with or without rituximab.

This retrospective cohort study described real-world treatment patterns and healthcare resource utilization (HCRU) of patients with warm autoimmune hemolytic anemia (wAIHA) initiating treatment with first-line (1L) oral corticosteroids (OCS) + rituximab (R) compared to 1L OCS. Patients with a wAIHA diagnosis code (D59.11) between 8/2020-3/2022 were identified using US pharmacy and medical claims databases. Patients initiating 1L OCS ± R were identified (date of initiation = 'index date') with a 1-year pre-index period and a variable (minimum 1-year) follow-up period. The final sample comprised 77 1L OCS + R patients and 400 1L OCS patients (~ 60% female, mean age > 64 years). Over the 1-year follow-up, HCRU was higher in the OCS + R cohort with higher mean number of physician office visits (22.9 and 14.4; p < 0.01), including hematology/oncology office visits, and higher utilization of rescue therapy (59.7% and 33.3%; p < 0.01), driven by higher use of injectable corticosteroids. Patients in OCS + R and OCS groups completed 1L therapy after a similar mean duration of 103.5 and 134.6 days, respectively (p = 0.24). In the majority of patients, second-line (2L) therapy was initiated at a similar timepoint: 66.2% OCS + R and 72.0% OCS cohorts (p = 0.31) initiated 2L in a mean of 218.3 and 203.2 days (p = 0.76) after the end of 1L treatment, respectively. The addition of rituximab in 1L did not extend the remission period, with most patients in both cohorts initiating 2L therapy within less than 1 year of completing 1L treatment. 1L OCS + R patients also had substantial HCRU burden. More effective novel therapies are needed to address the high unmet need in wAIHA.

Molecular pharmacology in complement-mediated hemolytic disorders.

In the last decade, a deeper understanding of the pathogenesis of complement mediated hemolytic disorders, such as paroxysmal nocturnal hemoglobinuria (PNH), cold agglutinin disease (CAD), warm type autoimmune hemolytic anemia (AIHA) with complement activation (wAIHA), and atypical hemolytic uremic syndrome (aHUS), paved the way to the therapeutic shift from purely supportive approaches to complement-targeted therapies. This resulted in a significant improvement in disease management, survival, and quality of life. In this review, we will provide a snapshot of novel therapies for complement-mediated hemolytic anemias with a focus on those ready to use in clinical practice. C5 inhibitors eculizumab and the long-acting ravulizumab, are the established gold standard for untreated PNH patients, whilst the C3 inhibitor pegcetacoplan should be considered for suboptimal responders to anti-C5 drugs. Several additional compounds targeting the complement cascade at different levels (other C5 inhibitors, factor B and D inhibitors) are under active investigation with promising results. In CAD, immunosuppression with rituximab remains the first-line. However, recently FDA and EMA approved the anti-C1s monoclonal antibody, sutimlimab, that showed dramatic responses and whose regulatory approval is soon awaited in many countries. Other drugs under investigation in AIHA include the C3 inhibitor pegcetacoplan, and the anti-C1q ANX005 for warm AIHA with complement activation. Finally, aHUS is an indication for complement inhibitors. Eculizumab and ravulizumab have been approved, whilst other C5 inhibitors, and novel lectin pathway inhibitors are under active investigation in this disease.

A rare case of complicated malaria presenting as warm autoimmune hemolytic anemia.

Autoimmune hemolytic anemia (AIHA) has been rarely reported worldwide or from India as the underlying cause of anemia in malaria. We hereby present a case of complicated Plasmodium falciparum malaria with concomitant warm AIHA in a 31-year-old male. Direct Antiglobulin Test (DAT) was positive and elution studies showed pan-agglutination reaction. Clinico-hematological and serological follow-up of the patient was done post artesunate treatment until day 9. We suggest that it is important to establish the immune basis of anemia in malaria patients for guiding the treatment plan for the clinicians and providing packed red blood cell transfusion if required.

In vitro Immunomodulatory Effects of Human Umbilical Cord-Derived Mesenchymal Stem Cells on Peripheral Blood Cells from Warm Autoimmune Hemolytic Anemia Patients.

INTRODUCTION: Autoimmune hemolytic anemia is a potentially lethal disease characterized by autoimmune hemolysis. Although human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) have been reported as a promising therapy, there is limited evidence regarding warm autoimmune hemolytic anemia (wAIHA) patients. This study aimed to investigate the potential therapeutic effects of hUC-MSCs via immune regulation in wAIHA patients. METHODS: Peripheral blood mononuclear cells (PBMCs) from 10 wAIHA patients and 8 healthy controls were isolated from peripheral blood and cultured for 3 days with or without the presence of hUC-MSCs; PBMCs were co-cultured with hUC-MSCs using Transwell assays. The supernatant cytokine levels were measured after culture through AimPlex Multiple Immunoassays for Flow, including IL-2, IL-4, IL-10, IFN-γ, TNF-α, and IL-17A. The percentages of regulatory T cells, regulatory B cells, and Th1/Th2 in PBMCs were also assessed before and after culturing. RESULTS: In the wAIHA group, hUC-MSCs could upregulate the Treg and Breg proportions after culturing for 3 days, and the Treg and Breg percentages increased after co-culturing with hUC-MSCs in the wAIHA group compared with PBMC cultured alone for 3 days (8.29 ± 8.59 vs. 6.82 ± 1.32, 3.82 ± 1.87 vs. 1.75 ± 1.20, respectively). Compared with the PBMC wAIHA group, the levels of TNF-α (2.13 ± 2.07 vs. 16.20 ± 21.13 pg/mL, p = 0.019) and IL-10 (10.51 ± 18.42 vs. 37.78 ± 44.20 pg/mL, p = 0.012) were significantly elevated in the PBMC + hUC-MSCs wAIHA group. CONCLUSION: The hUC-MSCs contributed to the increasing proportion of regulatory cell populations in PBMCs of wAIHA patients, thereby potentially regulating autoimmune response; thus, hUC-MSCs may be a promising approach for wAIHA treatment.

[Warm autoimmune hemolytic anemia and IgM-monoclonal gammopathy following BNT162b2 COVID-19 vaccine in a patient with splenic marginal zone lymphoma].

There is currently no evidence that a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccine might be associated with the development of autoimmune hemolytic anemia or disease progression in patients with mature B-cell neoplasm. Our patient was a 71-year-old man with indolent mature B-cell neoplasm who had been monitored for many years without treatment. After receiving the second dose of the BNT162b2 mRNA COVID-19 vaccine, he developed severe warm autoimmune hemolytic anemia. Although steroid therapy improved his anemia, he continued to develop IgM-monoclonal gammopathy, renal insufficiency, and splenomegaly. He was diagnosed with splenic marginal zone lymphoma after undergoing splenectomy. The splenectomy improved the patient's symptoms. We assessed his SARS-CoV-2 specific antibody response, but the patient's serologic response to the vaccine was impaired. In patients with mature B-cell neoplasm, a non-specific immune response after vaccination might be associated with paraneoplastic syndromes.

Thyroid storm and warm autoimmune hemolytic anemia.

Graves' disease is often associated with other autoimmune disorders, including rare associations with autoimmune hemolytic anemia (AIHA). We describe a unique presentation of thyroid storm and warm AIHA diagnosed concurrently in a young female with hyperthyroidism. The patient presented with nausea, vomiting, diarrhea and altered mental status. Laboratory studies revealed hemoglobin 3.9g/dL, platelets 171×109L-1, haptoglobin <5mg/dL, reticulocytosis, and positive direct antiglobulin test (IgG, C3d, warm). Additional workup revealed serum thyroid stimulating hormone (TSH) <0.01µIU/mL and serum free-T4 (FT4) level 7.8ng/dL. Our patient was diagnosed with concurrent thyroid storm and warm AIHA. She was started on glucocorticoids to treat both warm AIHA and thyroid storm, as well as antithyroid medications, propranolol and folic acid. Due to profound anemia and hemodynamic instability, the patient was transfused two units of uncrossmatched packed red blood cells slowly and tolerated this well. She was discharged on methimazole as well as a prolonged prednisone taper, and achieved complete resolution of the thyrotoxicosis and anemia at one month. Hyperthyroidism can affect all three blood cell lineages of the hematopoietic system. Anemia can be seen in 10-20% of patients with thyrotoxicosis. Several autoimmune processes can lead to anemia in Graves' disease, including pernicious anemia, celiac disease, and warm AIHA. This case illustrates a rarely described presentation of a patient with Graves' disease presenting with concurrent thyroid storm and warm AIHA.

Emergence of long-lived autoreactive plasma cells in the spleen of primary warm auto-immune hemolytic anemia patients treated with rituximab.

Primary warm autoimmune hemolytic anemia (wAIHA) is a rare autoimmune disease in which red blood cells are eliminated by IgG autoantibodies. We analyzed the antibody-secreting cells in the spleen and the peripheral blood of wAIHA patients in various contexts of treatment. Plasmablasts were observed in peripheral blood of newly diagnosed wAIHA patients and, accordingly, active germinal center reactions were present in the spleen of patients receiving short-term corticosteroid therapy. Long-term corticosteroid regimens markedly reduced this response while splenic plasma cells were able to persist, a fraction of them secreting anti-red blood cell IgG in vitro. In wAIHA patients treated by rituximab and who underwent splenectomy because of treatment failure, plasma cells were still present in the spleen, some of them being autoreactive. By using a set of diagnostic genes that allowed us to assess the plasma cell maturation stage, we observed that these cells displayed a long-lived program, differing from the one of plasma cells from healthy donors or from wAIHA patients with various immunosuppressant treatments, and more similar to the one of normal long-lived bone-marrow plasma cells. Interestingly, an increased level of B-cell activating factor (BAFF) was observed in the supernatant of spleen cell cultures from such rituximab-treated wAIHA patients. These results suggest, in line with our previous report on primary immune thrombocytopenia, that the B-cell depletion induced by rituximab promoted a suitable environment for the maturation and survival of auto-immune long-lived plasma cells in the spleen.

Warm autoimmune hemolytic anemia with mimicking anti-e specificity causing intravascular hemolysis in a chronic ITP patient.

A 12-year-old male child presented to the emergency room with three days history of cola-colored urine, mild icterus, dyspnea, palpitation and fatigue. He had a history of chronic ITP two years ago and had since been on steroid for maintenance of platelet count. He was subsequently diagnosed as a case of warm autoimmune hemolytic anemia. Laboratory investigations were suggestive of intravascular hemolysis, and on immuno-hematological evaluation it was diagnosed that the patient had autoantibody with mimicking anti-e specificity. The specificity of autoantibody was further confirmed by adsorption study. The patient was successfully managed by transfusion of Rh(e)-negative red cells,steroid and rituximab therapy. So an autoantibody with mimicking anti-e specificity was identified in this case, which was significant in clinical point of view.

Hepatolithiasis and Choledocholithiasis Secondary to Warm Autoimmune Hemolytic Anemia in the Setting of COVID-19 and Lupus.

Two major etiologies of hyperbilirubinemia include hemolysis and cholestasis. Although rare, the former can give rise to the latter through the formation of pigment gallstones and subsequent biliary tree obstruction. We report a case of a 57-year-old woman with systemic lupus erythematosus who presented with dyspnea and right upper quadrant abdominal pain. She was found to have hepatolithiasis and choledocholithiasis secondary to warm autoimmune hemolytic anemia in the setting of COVID-19. In patients with symptomatic anemia secondary to acute hemolysis and concomitant right upper quadrant abdominal pain, elevated hepatocellular laboratory results should prompt a high clinical suspicion for biliary tree pigment stones.

Antibody based therapeutics for autoimmune hemolytic anemia.

INTRODUCTION: Autoimmune hemolytic anemia (AIHA) treatment has been revolutionized by the introduction of target therapies, mainly monoclonal antibodies (MoAbs). AREAS COVERED: The anti-CD20 rituximab, which targets Ab production by B-cells, induces 80% of response in warm-type AIHA (wAIHA) and 50-60% in cold agglutinin disease (CAD). Other B-cell targeting MoAbs including ianalumab, povetacicept, and obexelimab are under active study. The anti-CD38 MoAb daratumumab has been used in several reports to target long-lived plasma-cells responsible for AIHA relapse, being effective even in multi-refractory cases. Anti-complement MoAbs will soon change the treatment paradigm in CAD; the anti-C1s sutimlimab rapidly increased Hb in more than 80% of the cases. Finally, MoAbs inhibiting the neonatal Fc receptor (FcRn), such as nipocalimab, can reduce the half-life of the pathogenic autoAbs, representing a promising treatment for wAIHA. EXPERT OPINION: MoAbs offer the potential to improve efficacy by reducing toxicity. However, there is a huge need for clinical trials exploring response duration rather than short-term efficacy. Complement inhibitors and anti-FcRns do not abrogate autoAb production and are being developed as long-term therapies. Thus, the combination of B-cell/plasma cell targeting drugs deserves to be explored. On the other hand, their rapid efficacy should be exploited for the acute AIHA phase.

Rare Loxoscelism-Associated IgG Coombs-Positive Hemolytic Anemia Treated Successfully With Systemic Corticosteroids.

Loxoscelism-associated hemolytic anemia is a rare but critical complication of brown recluse spider bites. It may lead to various systemic manifestations, including jaundice, dark urine, and anemia-related symptoms, in addition to general loxoscelism symptoms such as skin lesions, fever, myalgia, nausea, and vomiting. Prompt diagnosis is crucial and requires recognizing typical laboratory findings such as low hemoglobin, elevated lactate dehydrogenase, reduced haptoglobin levels, and possibly a positive direct antiglobulin test. There is no definitive guideline for the treatment of loxoscelism-associated hemolytic anemia. we report a case of a 32-year-old female who developed severe Coombs-positive autoimmune hemolytic anemia following a brown recluse spider bite, with an improvement in hemoglobin levels and hemolysis indices after the administration of systemic corticosteroids.

To Transfuse or Not to Transfuse: A Case of Unresectable Renal Cell Carcinoma-Induced Warm Autoimmune Hemolytic Anemia.

Warm autoimmune hemolytic anemia (WAIHA) is a rare disease. Roughly half of all cases are considered either primary or idiopathic. The remaining cases are typically secondary to a drug reaction or an underlying disease state such as malignancy, infection, or chronic autoimmune disease. Treatments for WAIHA include corticosteroids, intravenous immunoglobulin (IVIG), rituximab, and splenectomy. We present a case of WAIHA with underlying clear cell renal cell carcinoma (RCC) that was unresectable, creating a difficult treatment course. A 76-year-old male with recently diagnosed clear cell RCC was admitted with symptomatic WAIHA and significant hemodynamic instability. Over the course of his admission, he received 25 blood transfusions, erythropoietin, methylprednisolone, IVIG, rituximab, and mycophenolate mofetil in an attempt to control his disease state. He suffered end-organ damage in the form of heart failure with reduced ejection fraction. He was deemed too unstable for RCC resection or interventional cardiac procedures. Determining an appropriate transfusion threshold proved to be a noteworthy challenge. His hemoglobin eventually stabilized to 7.4 g/dL upon discharge over the course of 27 days of treatment. The underlying cause of his WAIHA was believed to be most likely secondary to RCC. WAIHA may have a prolonged treatment course with high risk of mortality if the underlying cause is not resolvable. If this is the case, it can be difficult to determine a hemoglobin transfusion threshold that maintains normal vital signs while minimizing the risk of transfusion-associated circulatory overload (TACO) and transfusion-related acute lung injury (TRALI). Prolonged hemodynamic instability may result in end-organ damage. For our patient, we aimed for a hemoglobin transfusion threshold of 5.0-6.0 g/dL based on his mean arterial pressure (MAP), heart rate, and subjective symptoms.

Genome-wide DNA methylation profiles analysis in primary warm autoimmune hemolytic anemia patients.

BACKGROUND: Autoimmune hemolytic anemia (AIHA) is caused by auto-antibodies, secreted by overactivated B cells, directed against self-red blood cells, resulting in hemolysis. It found that aberrant DNA methylation in B cells can induce the production of autoantibodies. Therefore, we attempted to explore if similar aberrant DNA methylation occur in AIHA patients. METHODS: A 49-year-old female wAIHA patient and a 47-year-old female healthy control (HC) were enrolled. Peripheral blood (PB) B cells DNA was extracted. After constructing genomic libraries, bisulfite genomic sequencing (BSP) and DNA methylation profiles were analyzed. BSP was verified using PB B cells from 10 patients with hemolysis, 10 patients with hemolytic remission, and 10 healthy controls (HCs) by Methylation-specific PCR. RESULTS: Total DNA methylation of whole-genome C bases (4.8%) and CG type bases (76.8%) in wAIHA patient were lower than those in the HC (5.3 and 82.5%, respectively) (p = 0.022 and p < 0.001). DNA methylation of C bases and CG type bases in whole-genome regulatory elements, such as coding sequence, up2Kb and down2Kb in the patient were also lower than those in the HC (p = 0.041, p = 0.038, and p = 0.029). 30,180 DNA-methylated regions (DMRs) on all 23 chromosomes were identified. DMR-related genes were mainly involved in the Rap1, phospholipase D, HIF-1, calcium, vascular endothelial growth factor (VEGF) and Ras signaling pathways. CONCLUSION: The DNA methylation spectrum of B cells in AIHA patients is different from that of HC, and the proportion of hypo-methylation regions is higher than that of HC. DMR-related genes are mainly related to some signaling pathways.

Cytokine polymorphisms in patients with autoimmune hemolytic anemia.

Autoimmune hemolytic anemia (AIHA) is due to autoantibodies with or without complement activation and involves cellular and cytokine dysregulation. Here, we investigated cytokine single-nucleotide polymorphisms (SNPs) of TNF-α, TGF-ß1, IL-10, IL-6, and IFN-γ, along with their serum levels. The former were related to hematological parameters, therapy, and clinical outcome. The study included 123 consecutive patients with primary AIHA [77 warm AIHA and 46 cold agglutinin disease (CAD)], followed up for a median of 49 months. Results show that the allelic frequency of TNF-α -308 G/A polymorphisms was significantly lower in patients versus controls. Moreover, the genotypic frequency of TNF-α -308G/A and TGF-ß gene codon 25 G/C genotypes was significantly lower in patients versus controls. Considering cytokine SNP genotypes associated with different gene expression levels, TNF-α high gene expression was significantly more frequent in patients, TGF-ß and IL-10 high gene expression was higher in patients with more severe anemia, and TGF-ß high gene expression was higher in patients with active disease. Considering treatment, TNF-α and TGF-ß high gene expression was more frequent in multitreated patients and particularly in CAD. It may be speculated that this genetic predisposition to a stronger inflammatory response may result in a greater immune dysregulation and in a relapsed/refractory disease. Regarding cytokine serum levels, TNF-α and TGF-ß were significantly lower, and IL-10 and IL-6 were significantly higher in patients versus controls, underlying the complex interplay between genetic background and disease features.

Autoimmune Hemolytic Anemia Following Uncomplicated Spinal Surgery: A Report and Brief Review.

This report and literature review describes a case of a Coombs test-positive warm antibody autoimmune hemolytic anemia (AIHA) in a patient following routine spinal surgery without complications. This is the first reported case of symptomatic direct Coombs test-positive warm antibody AIHA developing in a neurosurgical patient. The patient is a 73-year-old female with left radicular leg pain who developed warm antibody AIHA following standard uncomplicated spinal surgery. A positive direct Coombs test confirmed the diagnosis in combination with characteristic laboratory values. The patient did not have any significant predisposing risk factors. On postoperative day (POD) 23, she presented with fatigue and characteristic laboratory values of decreased hemoglobin, elevated bilirubin, lactate dehydrogenase, and decreased haptoglobin. Hematology initiated and monitored appropriate treatment and proposed that the working hematologic diagnosis is stress-induced AIHA secondary to recent spinal surgery. The patient recovered well from a neurosurgical perspective and reported no neurosurgical complaints during the last follow-up. A female presenting with left radicular leg pain developed symptomatic anemia following uncomplicated spinal surgery. A positive direct Coombs test in combination with characteristic laboratory values confirmed the diagnosis of warm antibody AIHA.

The First-Reported Case of Drug-Induced Hemolytic Anemia by Piperacillin-Tazobactam in a Premature Neonate: A Case Report and Literature Review.

Drugs can have a wide array of effects on hematological cells, including red blood cells (RBCs), white blood cells (WBCs), and platelets. Drug-induced hemolytic anemia (DIHA) can be explained by three different pathophysiological mechanisms. We present a case of a premature neonate born at 34 weeks gestation who was admitted to the neonatal intensive care unit (NICU). He developed respiratory difficulty with mottled skin and was suspected to have bacterial sepsis due to necrotizing enterocolitis (NEC). The patient was eventually started on a broad-spectrum antibiotic, piperacillin-tazobactam. On day eight, the patient started developing jaundice and his hemoglobin level dropped from 12.1 to 8.2 mg/dL. His direct antiglobulin test (DAT) was strongly positive. The patient was suspected to have DIHA. Piperacillin-tazobactam is a commonly used antibiotic for neonatal sepsis, but its potential to cause DIHA in neonates is not well-established. Our case highlights the importance of considering piperacillin-tazobactam as an unrecognized contributor to neonatal jaundice and a potential cause of DIHA in neonates. Further research is needed to explore the extent of its involvement in this condition. Physicians should be cautious when administering this drug to neonates and be aware of the possibility of hemolysis and jaundice.

Multifactorial jaundice and pigmented choledocholithiasis secondary to warm autoimmune hemolytic anemia and alcoholic cirrhosis.

A 67-year-old man with a history of alcoholic cirrhosis presented with acute abdominal pain. His total bilirubin was 43.8 mg/dL and fractionated to a direct bilirubin of 32.7 mg/dL. A warm agglutinin IgG1 antibody was positive, and abdominal magnetic resonance imaging detected an obstructing stone at the level of the sphincter of Oddi. Two pigmented gallstones were removed by endoscopic retrograde cholangiopancreatography. His total bilirubin decreased to 24.6 mg/dL the following day, and he was initiated on 20 mg of prednisone for his autoantibody.

New Therapies for the Treatment of Warm Autoimmune Hemolytic Anemia.

In this review article we provide a critical insight into recent reports evaluating innovative therapies for warm type autoimmune hemolytic anemia (wAIHA). Among published articles, we selected two reports on the use of the proteasome inhibitor bortezomib in association with dexamethasone or rituximab, one study on the spleen tyrosine kinase inhibitor fostamatinib, and a retrospective study on recombinant erythropoietin (rEPO). Among recent scientific communications, we discussed a report on the phosphoinositide 3-kinase delta inhibitor (PI3Kδi) parsaclisib. All studies highlighted a good efficacy although to be confirmed in larger trials and with limitations due to the heterogeneity of wAIHA patients enrolled, the small number of subjects, the concomitant medications allowed, and the short follow-up. Ongoing trials include new B-cell/plasma-cell targeting agents such as the Bruton tyrosine kinase inhibitors ibrutinib and rilzabrutinib, and the anti-CD38 MoAbs daratumumab and its analogue isatuximab. Further drugs in clinical trials target the complement cascade in wAIHA with complement activation, such as the C3 inhibitor pegcetacoplan and the C1q inhibitor ANX005. Finally, an interesting and non-immuno-toxic strategy is to remove the pathogenic autoantibodies via blocking the neonatal Fc receptor, by intravenous nipocalimab and subcutaneous RVT-1401. Such novel agents targeting the several immunopathological mechanisms acting in wAIHA and their possible combination, will increase the therapeutic armamentarium and possibly fill the gap of wAIHA relapsed after/refractory to rituximab. Moreover, these new target therapies may represent a tool for the unmet need of very acute cases.

Novel Monoclonal Antibody Therapy in a Patient With Treatment-Refractory Warm Autoimmune Hemolytic Anemia.

In autoimmune hemolytic anemia (AIHA), hemolysis is the hallmark symptom. Cold agglutinin disease (CAD) and warm autoimmune hemolytic anemia (wAIHA) are the two major forms of AIHA. Hemolysis is complement dependent in CAD, whereas wAIHA is a partially complement-mediated disorder. At the time of writing, sutimlimab-jome is the only FDA-approved monoclonal antibody in the treatment of CAD. In a case of severe treatment-refractory wAIHA, a two-week course with sutimlimab-jome resulted in a sustained decrease in total bilirubin level and a notable reduction in transfusion requirement, suggesting that it is also effective in the treatment of wAIHA.

Endogenous carbon monoxide due to hemolytic anemia: A forensic red herring.

Carbon monoxide (CO) toxicity associated with exposure to an environmental, exogenous source, is routinely investigated in the field of forensics. Paramedics responded to the home of a 60-year-old woman who complained of persistent nausea, dizziness, and fatigue. Her initial carboxyhemoglobin (COHb) saturation was 25% as measured by paramedics in the field via pulse CO-oximetry (SpCO) and was, 2 hours later, confirmed by hospital laboratory spectrophotometric analysis to be 16% after initial treatment in the emergency department. The clinical presentation of environmental CO exposure and subsequent death notification to the North Carolina Office of the Chief Medical Examiner prompted an extensive investigation into the suspected residential source of CO, which ultimately ruled out all exogenous sources. The medicolegal death investigator later discovered an updated hematology consultation note, which determined the actual source of the CO to be endogenously produced from disease. Herein, we report an unusual fatality involving enhanced endogenous CO production caused by warm autoimmune hemolytic anemia. This unique case report and brief literature review of disease-related elevation of endogenous CO will shed light on this lesser-known phenomenon alerting the forensic community to its potential occurrence and need for consideration when sources of environmental exposure have been exhausted.