Introduction: The purpose of this case presentation is to demonstrate that although a complex diagnosis may underlie HTP, this may be, only one of the many causes that determine it.

Methods: We present the case of a 62 year old male, di-agnosed with Klippel-Trenaunay syndrome (KTS) sin-ce 2005, with a gigantic arteriovenous aneurysm in the right pelvic quadrant and right femoral arteriovenous malformation with fistula, who is referred to our cardio-logy department for evaluation of symptomatic pulmo-nary hypertension (PH). Moderate PH was described since 2005 and was considered secondary to KTS. The purpose of this case presentation is to demonstrate that we should not stop at the first complex diagnosis, as se-veral diseases can coexist in a patient and could explain PH.Clinical evaluation of our patient found lower limb asymmetry with right limb edema with ocra dermatitis, arrhythmic heart sounds, tricuspid systolic heart mur-mur with fixed S2 splitting, pelvic systolic murmur and continuous murmur at calf level. An elevated BNP (245 pg/ml) was measured. The 2D transthoracic echocar-diography showed several abormal findings: enlarged right cavities with right ventricular global dysfunction (RVFAC 34%), severe tricuspid regurgitation, PH of 78 mmHg. In order to asses more carefully the interatrial septum, transesophageal echocardiography was perfor-med, and discovered a double orifice ostium secundum atrial septal defect (ASD) with a total area of 2.6 sqcm and predominant left-to-right shunt. Pelvic and lower limb angioCT confirmed large dilation of right exter-nal iliac vein and artery leading to a tumoral vascular mass, as well as aneurysmal right femoral artery with arteriovenous fistula at this level. Moreover, evaluation of the right lower limb revealed old venous thrombosis at popliteal and femoral level in a patient only recently anticoagulated for atrial fibrillation.

Results: Therefore, 3 etiologies are possible for the PH: large arteriovenous fistula in the right lower limb with high flow, large double ostium secundum ASD not clo-sed until adulthood, small pulmonary embolisms from non-anticoagulated deep vein thrombosis. Based on further findings of cardiac catheterization and thoracic CT, the therapeutic algorithm will take into conside-ration closing the ASD and/or pulmonary vasodilator medication for PH. Of note, presence of the arterio-ve-nous malformation led to the differential diagnosis of KTS and final classification as Parkes Weber syndrome (PWS).

Conclusions: Pulmonary hypertension is a complex disease with many possible etiologies. While the fin-ding of large arteriovenous malformation and fistula in this patient led many years ago to thinking that this was the only PH etiology, we were able to prove that PH is pluri-etiologic due to PWS, double ostium secundum ASD, with a thromboembolic cause to be taken into consideration, each leading to specific therapies.