A43-09 Mycoplasma Pneumoniae Presenting as Acute Hypoxemic Respiratory Failure With Diffuse Micronodular Pattern and Concurrent ColdAgglutinin Hemolytic Anemia

Abstract Background Cold-agglutinin hemolytic anemia is an uncommon extrapulmonary manifestation of Mycoplasma pneumoniae that can precipitate rapid, clinically significant hemolysis. We report a case emphasizing serial laboratory trends and objective hematologic data alongside a striking airway-scentric chest CT appearance that initially suggested miliary-type processes. Case Presentation A 55-year-old man with type 2 diabetes presented with progressive dyspnea after a three-week prodrome of cough, night sweats, fatigue, and 10 lbs unintentional weight loss. He had an outpatient telehealth visit and received a short course of oral steroids without symptomatic improvement. On arrival to the outside hospital, he was afebrile, markedly tachycardic (130 bpm), tachypneic, hypoxemic on nasal cannula, and leukocytotic (WBC 21. 9 × 10⁹/L). Contrast chest CT demonstrated diffuse interstitial micronodular/tree-in-bud opacities resembling a miliary pattern with mild mediastinal lymphadenopathy; the initial differential included miliary tuberculosis, disseminated fungal infection, Mycobacterium avium-intracellulare, and sarcoidosis. Over 48-72 hours his hemoglobin declined precipitously to a nadir of approximately 6. 1 g/dL with marked reticulocytosis (13. 1%, abs ∼200 × 10⁹/L) and an elevated LDH of 565 U/L, consistent with acute hemolytic anemia. He received packed RBC transfusion (s) at the referring center and was transferred to tertiary care for hematology evaluation and potential need for invasive therapies given ongoing hemolysis requiring transfusions. Respiratory PCR was positive for Mycoplasma pneumoniae, and Mycoplasma IgM was also positive; direct antiglobulin testing later returned positive for a cold autoantibody, confirming cold-agglutinin involvement. He was managed with doxycycline for antimicrobial therapy against Mycoplasma and transfusion for symptomatic anemia (post-transfusion Hgb ∼7. 5 g/dL) within a coordinated multidisciplinary approach involving hematology and infectious disease. Planned plasmapheresis and immunosuppressive therapy were postponed when clinical and laboratory improvement began, and no invasive immunomodulation was required. The patient was discharged medically stable, remained stable on short-interval CBC monitoring, and follow-up chest CT demonstrated resolution of the prior micronodular/tree-in-bud abnormalities. Discussion and Conclusion This case correlates a diffuse micronodular/tree-in-bud CT phenotype that mimicked miliary-type processes with fulminant hemolytic anemia and cold-agglutinin positivity in the setting of Mycoplasma pneumoniae. Temporal laboratory trends and the clinical course underscore the importance of early recognition of hemolysis in atypical respiratory illness and of integrating imaging, hematologic data, and microbiologic results to guide management. Prompt targeted antimicrobial therapy and close multidisciplinary coordination can avert invasive hematologic escalation and facilitate recovery. This abstract is funded by: none