Symptomatic diffuse pulmonary meningotheliomatosis with persistent diffusing-capacity impairment.

Diffuse pulmonary meningotheliomatosis (DPM) is an ultrarare diffuse parenchymal lung disease in which pulmonary meningothelial-like nodules produce a miliary radiographic pattern. Most reported cases are asymptomatic and incidentally detected, and longitudinal physiologic data in symptomatic patients remain scarce. A 52-year-old postmenopausal never-smoker presented with three months of progressive exertional dyspnea. High-resolution computed tomography showed innumerable small bilateral nodules in a diffuse, random miliary distribution. A non-dedicated chest CT obtained approximately three months earlier had not described nodules. Serologic and microbiologic workup was unrevealing, and bronchoscopy was nondiagnostic. Video-assisted thoracoscopic wedge resection showed bland spindle-cell nests, and immunohistochemistry established DPM. Serial pulmonary function testing showed moderate restriction with reduced diffusing capacity and alveolar volume. During follow-up, forced vital capacity and six-minute walk distance improved, while static volumes and the diffusing-capacity deficit persisted. Severe obesity likely contributed to the restrictive defect. At reduced alveolar volume, the transfer coefficient (KCO) remained lower than expected for pure extrapulmonary restriction, raising the possibility of an intrinsic pulmonary component. However, obesity, possible pulmonary vascular disease, and other factors precluded attribution of these abnormalities to DPM alone. Management was conservative, without corticosteroids, and the disease burden remained radiographically stable. Symptomatic DPM may show functional improvement despite persistent restriction and impaired diffusing capacity. DPM should be considered among the causes of diffuse miliary opacities when imaging and serologic evaluation are nondiagnostic.