A40-46 Symptomatic Diffuse Pulmonary Meningotheliomatosis: A Case of Rapidly Progressive Dyspnea

Abstract Introduction Diffuse pulmonary meningotheliomatosis (DPM) represents an exceedingly rare interstitial lung disease characterized by the widespread proliferation of meningothelial-like cells within the pulmonary parenchyma, with about 44 reported cases in the literature. Typically, these meningothelial-like nodules are discovered incidentally during histological examination of lung biopsies, often presenting as innumerable minute pulmonary meningothelial-like nodules (MPMNs). While frequently asymptomatic and incidentally detected on imaging, DPM can, in rare instances, manifest with significant clinical symptoms such as rapidly progressive dyspnea. This case report highlights a symptomatic presentation of DPM, emphasizing the need for inclusion of this rare entity in the differential diagnosis of diffuse parenchymal lung diseases. Case Presentation A 52-year-old female with type 2 diabetes mellitus, obesity (BMI 40), and numerous other comorbidities presented with 2-months of rapidly progressive exertional dyspnea. Initial cardiac evaluation was inconclusive. Due to her persistent dyspnea, pulmonary function tests were performed, which showed a moderate restrictive pattern (FVC 59% predicted, TLC 4.15L) and moderate diffusion impairment (DLCO 58% predicted). A high-resolution CT chest revealed diffuse miliary opacities not present three months prior. Surgical lung biopsy revealed MPMNs. Immunohistochemistry was positive for CD56, epithelial membrane antigen, and progesterone receptor, confirming DPM. Discussion/Conclusion This case challenges the perception of DPM as a uniformly benign and indolent condition. This patient’s rapid clinical deterioration, restrictive physiology, and new radiological progression demonstrate that DPM can manifest as an aggressive phenotype requiring prompt diagnostic evaluation. While DPM is generally considered reactive with a favorable prognosis, this presentation underscores the necessity of including DPM in the differential diagnosis of diffuse miliary opacities, especially in cases with rapid onset of symptoms. Figure 1: Top left: MPMNs, described as multiple perivenular whirling nests of bland spindle/oval cells with pale cytoplasm expanding the alveolar septa. Rest of the images: IHC studies showing positivity for: the Progesterone receptor (PR, top right), epithelial membrane antigen (EMA, bottom left), and CD56 (bottom right) This abstract is funded by: None