A Case of Late-Onset Acute Pulmonary Sarcoidosis Exacerbation After 26 Years of Clinical Stability.

Pulmonary sarcoidosis is a systemic granulomatous disease with a variable clinical course. While many cases resolve spontaneously, a subset of patients may develop chronic disease or experience acute pulmonary exacerbations. Such exacerbations typically occur within the first decade after diagnosis, and late-onset exacerbations after a prolonged quiescent phase are exceedingly rare. We present the case of a 59-year-old Japanese man who developed acute pulmonary exacerbation of sarcoidosis (APES) 26 years after being diagnosed with stage I disease. He had remained clinically stable without systemic treatment and had only been followed for ocular involvement. He presented with progressive exertional dyspnea over four months, followed by fever and resting dyspnea. High-resolution computed tomography revealed bilateral ground-glass opacities, mediastinal lymphadenopathy, and traction bronchiectasis. Laboratory tests showed elevated lactate dehydrogenase (LDH), Krebs von den Lungen-6 (KL-6), and soluble interleukin-2 receptor (sIL-2R) levels. Bronchoalveolar lavage demonstrated lymphocytosis, and transbronchial lung cryobiopsy confirmed non-caseating granulomas. Infectious and autoimmune etiologies were excluded. The patient was diagnosed with APES and treated with systemic corticosteroids, including an initial pulse therapy followed by tapering oral prednisolone. His oxygenation improved significantly, and supplemental oxygen was no longer required at rest by hospital day 24, although desaturation persisted with exertion. Follow-up imaging showed partial radiologic improvement, along with newly developed pneumomediastinum. This case underscores the potential for sarcoidosis to reactivate even after decades of clinical remission. Long-term follow-up is essential, particularly in patients with fibrotic changes or extrapulmonary involvement. Early recognition and prompt management of late-onset APES may help prevent irreversible pulmonary damage.