Pulmonary small lymphocytic lymphoma combined with paraneoplastic pemphigus and bronchiolitis obliterans: a case report.

BACKGROUND: Paraneoplastic pemphigus is a rare autoimmune mucocutaneous disease often associated with neoplasms. When complicated with bronchiolitis obliterans, it can lead to irreversible pulmonary dysfunction and carries a high risk of mortality. We report a case of pulmonary small lymphocytic lymphoma combined with paraneoplastic pemphigus and bronchiolitis obliterans, aiming to increase clinical awareness of this condition and promote early diagnosis and treatment. CASE PRESENTATION: We report the case of a 69-year-old male who initially presented with oral lichen planus and developed cough and dyspnea on exertion three months later. Blood gas analysis revealed hypoxemia, and pulmonary function tests showed extremely severe mixed ventilatory dysfunction. Chest imaging demonstrated thickened walls of peripheral bronchioles, centrilobular nodules, and partial bronchiectasis in both lower lobes. Laboratory tests were positive for anti-desmoglein 3 antibodies. Ultimately, a mediastinal biopsy confirmed the diagnosis of pulmonary small lymphocytic lymphoma. The patient received two cycles of treatment with Orelabrutinib combined with Obinutuzumab, after which his oral lichen planus and dyspnea improved. CONCLUSIONS: Clinicians should be alert to the possibility of paraneoplastic pemphigus in patients presenting with refractory oral mucosal lesions. Especially when accompanied by unexplained pulmonary imaging abnormalities and dyspnea, bronchiolitis obliterans should be considered. Recognizing the early predictive value of oral lesions is crucial for avoiding misdiagnosis or delayed diagnosis, enabling timely intervention and improved patient outcomes.