Abstract Introduction Organizing pneumonia (OP) is a histopathologic pattern of interstitial lung disease (ILD) marked by intra-alveolar granulation tissue and disrupted repair following lung injury. While often idiopathic, OP may represent an early or isolated manifestation of connective tissue disease-associated ILD (CTD-ILD). Diagnosing autoimmune ILD is particularly challenging when systemic features are absent and traditional serologic markers are negative. Prompt recognition and immunosuppression are critical in rapidly progressive cases. Case Presentation A 68-year-old woman with eczema and a remote seizure disorder presented with worsening dyspnea over three months. Initial chest CT revealed patchy bilateral airspace opacities, and transbronchial biopsy confirmed an organizing pneumonia pattern. Despite outpatient corticosteroids, her respiratory status deteriorated. In the emergency department, she was tachypneic, tachycardic, and hypoxic (SpO2 in the low 80s on room air), requiring high-flow nasal cannula (50 L/min, FiO2 80%). Repeat imaging revealed worsening multifocal consolidations and the development of new bilateral pleural effusions. Thoracentesis yielded transudative fluid. An infectious workup was negative. Autoimmune testing revealed positive SSA-52 (Ro52) and elevated aldolase, though ANA, ANCA, RF, and anti-CCP were negative. She had no clinical features of systemic autoimmune disease: no rash, arthritis, Raynaud’s, myositis, sicca, or fevers. Given her rapid decline, she received pulse-dose IV methylprednisolone followed by intravenous immunoglobulin (IVIG). Her oxygen requirements improved, and she was gradually weaned to nasal cannula. Discussion This case highlights a lung-predominant autoimmune ILD presenting with an organizing pneumonia pattern, in the absence of systemic connective tissue disease manifestations. While OP is often termed “cryptogenic,” secondary causes—especially autoimmune—must be carefully considered when suggestive serologies are present. The presence of SSA-52 and elevated aldolase raised suspicion for an inflammatory myopathy-associated ILD, such as antisynthetase syndrome or ILD-first overlap syndromes. Many patients with autoimmune ILD present without myositis or joint involvement, and some never develop systemic signs. These “lung-limited” phenotypes are increasingly recognized and may precede classic features by months to years. Early initiation of immunosuppressive therapy is essential in rapidly progressive cases. IVIG may offer benefit in antibody-positive ILDs, especially when muscle involvement is subclinical or evolving. Conclusion Organizing pneumonia should not always be presumed idiopathic. In patients with progressive ILD and subtle serologic clues—even without systemic symptoms—clinicians must maintain a high index of suspicion for autoimmune disease. Recognizing lung-dominant CTD-ILD early and initiating timely immunosuppression can significantly improve outcomes. This abstract is funded by: none
Bartholomew et al. (Fri,) studied this question.