Pulmonary sarcoidosis with suspected bone marrow involvement presenting as severe thrombocytopenia: a case report.

BACKGROUND: Sarcoidosis is a multisystem granulomatous disorder of unclear etiology, with the lungs and mediastinal lymph nodes being the most frequently involved sites. Bone marrow involvement in sarcoidosis is extremely rare, and its presentation with severe thrombocytopenia as the dominant hematological abnormality is even more uncommon, which often results in clinical misdiagnosis. We report a case of pulmonary sarcoidosis with suspected bone marrow involvement presenting as severe thrombocytopenia, aiming to supplement the clinical evidence for such rare manifestations and provide a reference for clinical diagnosis and management. CASE PRESENTATION: A 60-year-old male was admitted to our hospital due to chest tightness, wheezing, and dyspnea lasting more than six months. Laboratory investigations revealed severe thrombocytopenia (platelet count 8×109/L), and chest computed tomography (CT) demonstrated enlargement of mediastinal and bilateral hilar lymph nodes, along with bilateral pulmonary infiltrates. Pulmonary function tests showed a restrictive ventilatory defect accompanied by severe impairment of pulmonary diffusion capacity. Bone marrow aspiration and biopsy suggested impaired platelet production by megakaryocytes, whereas endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) of mediastinal lymph nodes confirmed non-caseating granulomas, consistent with the diagnosis of sarcoidosis. The patient was diagnosed with stage II pulmonary sarcoidosis complicated with suspected bone marrow involvement and was treated with oral prednisone acetate. Following one month of standardized treatment, the patient’s respiratory symptoms were completely relieved, pulmonary lesions and mediastinal lymphadenopathy were significantly improved, and the platelet count recovered to 75×109/L. During a six-month follow-up period, the patient remained asymptomatic, with stable platelet counts and no adverse events observed. CONCLUSION: Severe thrombocytopenia may serve as a rare manifestation of pulmonary sarcoidosis with bone marrow involvement. When sarcoidosis is accompanied by unexplained hematological abnormalities, the possibility of bone marrow involvement should be taken into consideration. A comprehensive assessment integrating clinical manifestations, imaging findings, pathological results, and treatment response is essential for accurate diagnosis and prevention of misdiagnosis. Early and standardized glucocorticoid therapy can yield significant therapeutic outcomes in such cases.