Cowden Syndrome (CS) is a rare autosomal dominant disorder caused by germline PTEN pathogenic variants. Clinical diagnostic criteria and frequencies of clinical features are not well established. Vascular manifestations are rare but have been previously described in CS, mainly arteriovenous fistulas, vascular tumours, and pseudoaneurysms. Anterior tibial artery (ATA) pseudoaneurysms are rare and usually occur due to iatrogenic injuries such as orthopaedic procedures, blunt or penetrating trauma and sports injury. Its occurrence adds significant morbidity and can be potentially limb threatening - treatment, open or endovascular, should be considered immediately.

The case report includes gathered information from electronic medical records, surgical reports and the picture archiving system.

We report a 37-year-old men with a past medical history of total thyroidectomy due to papillary carcinoma at the age of 26. He was transferred from another institution due to the suspicion of left acute lower limb ischemia. The patient complained of pretibial left leg pain, as well as numbness and coldness of the foot. He had no prior history of intermittent claudication, no history of trauma and no previous lower limb surgery. Physical examination revealed a pale and cold foot, increased tenderness of the anterior leg compartment with moderate tension, limited dorsiflexion of the foot, no sensitive deficits, widened popliteal pulse, palpable posterior tibial pulse and absent pedal pulse. Doppler ultrasound exposed a pseudoaneurysm at the level of the popliteal fossa unrelated to the popliteal vessels, and an occluded ATA. CT angiography revealed a high bifurcation of the popliteal artery and a 30mm pseudoaneurysm related to the ATA, 21mm after its origin, creating a slight compression of the tibioperoneal trunk. Distal ATA and dorsalis pedis were occluded. Asides for rhabdomyolysis, analytical and bacteriological were unremarkable. Urgent surgery was proposed. Left anterograde ultrasound-guided femoral access was obtained and a 6F sheath placed. Initial diagnostic angiography confirmed CT's findings - dorsalis pedis artery and ATA were occluded distal to the pseudoaneurysm, with normal anatomy and patency of the remaining leg vessels. ATA occlusion just proximal to the pseudoaneurysm was achieved using an 8mm Amplatzer™ Vascular Plug 4 (AVP 4). Proper pseudoaneurysm exclusion was confirmed without any retrograde filling through the ATA. Decompressive fasciotomies were required for the anterior compartment due to severe muscle tension. The patient had a positive clinical evolution during admission, without any ischemic symptoms and improvements in foot mobility and autonomous ambulation. Fasciotomy wound was left for secondary closure and submitted to skin grafting two months later, achieving complete healing three months after initial surgery. During admission, and asides from the past thyroid carcinoma, several clinical symptoms and findings were noted: macrocephaly, oesophageal acanthosis nigricans, numerous stomach polyps, oral verrucous lesions and learning disabilities. Careful history taking revealed a heavy familiar past of early neoplasms on the mother side. The family was referred for Genetical consultation for diagnostic confirmation and proper follow-up.

CS is associated with vascular anomalies, most commonly arteriovenous fistulas. Other forms of vascular anomalies are rare and have seldom been described in the literature. This report concerns an ATA pseudoaneurysm has the presentation feature leading to CS diagnosis, allowing proper referral and family surveillance.

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