Abstract The case of one patient is described: 78–year–old, obese, suffering from type II diabetes mellitus and arterial hypertension who complained of mild exertional dyspnea for one year. On ECG sinus rhythm 80 bpm, negative T wave from V1 to V4, right bundle branch block. He was sent to the emergency unit for further investigations. Here the blood chemistry results: D–dimer 1761 (normal <250 ng / ml), NT pro–BNP 9312 (normal <93 ng / l), troponin 21 (normal <14 ng / ml); pulmonary CT angiography demonstrated filling defects referable to bilateral lobar, segmental and subsegmental bilateral thromboembolism. The estimated PASP was 90 mmHg with AcT 55 msec and the presence of a mid–systolic notch on the pulmonary flow profile. A diagnosis of intermediate–high risk PE was made and, according to the local PDTA, written informed consent was obtained, the patient underwent treatment with percutaneous thrombectomy with loco–regional ultrasound–assisted thrombolysis (USAT–rtPA 24 mg in 12 hours). The RV / LV ratio was slightly reduced (1.1) and so was the estimated PASP (60 mmHg). He performed a lung perfusion scan with the detection of areas of diffuse pulmonary hypoperfusion. He was discharged on February 28, 2021, on therapy with Dabigatran 150 mg BID. 3 months later he carried out a cardiological check–up: he was in NYHA II class; the echocardiogram showed RV hypokinesia, TAPSE 15 mm, PASP 76 mmHg. In the suspicion of chronic thromboembolic pulmonary hypertension (CTEPH), he was sent to a HUB centre (Pavia) for a clinical assessment. Several tests were carried out to confirm the diagnosis of CTEPH and on 29 September 2021, the patient underwent bilateral pulmonary endarterectomy. Conclusion The case describes a patient with an episode of acute pulmonary embolism on a pre–existing unrecognized thromboembolic pulmonary hypertension, which partially benefited from percutaneous thrombectomy. Cases of CTEPH are infrequent; however, they must be recognized and sent, for a thorough evaluation, to an expert centre, to start the appropriate diagnostic therapeutic path, as in the case reported.