[Third-degree AV block and generalized lymphadenopathy: an interdisciplinary challenge].

We report here on a patient with a rare pulmonary cause of third-degree AV block who was initially referred to us for further investigation of generalized lymphadenopathy. He had a history of third-degree AV block in December 2023, where etiology could not be determined even after extensive diagnostic workup. Following a pulmonary embolism that occurred afterwards, incidental findings of unclear generalized lymphadenopathy as well as splenic and liver lesions were seen on CT scan.For further investigation, a bronchoscopic ultrasound-guided biopsy of the mediastinal lymph nodes was performed. Histological workup revealed non-necrotizing epithelioid cell granulomas, consistent with sarcoidosis. The patient's case was discussed at our multidisciplinary conference for interstitial lung diseases (ILD board).In summary, based on all findings, a diagnosis of pulmonary sarcoidosis with spleen, liver, and heart involvement was made. Retrospectively, a cardiac manifestation of the diagnosed sarcoidosis was most likely already present in December 2023, when the AV block was diagnosed.Due to the multiorgan manifestation, a combination therapy of prednisolone and methotrexate for at least one year was recommended.Sarcoidosis is a granulomatous disease of unknown etiology and, as a multisystem disease, exhibits various manifestations with heterogeneous presentations. This case illustrates that cardiac sarcoidosis should always be considered as a differential diagnosis in the case of a new-onset AV block.