Idiopathic brachial artery true aneurysm in 28-year-old female

True brachial artery aneurysms (BAA) are considerably rare dilatations of the brachial artery including all three layers of the vessel wall which can have potentially devastating limb threatening complications 4 . The gold standard of treatment remains as open surgical resection, oftentimes requiring utilization of autogenous or prosthetic conduit. We present a case of idiopathic true left brachial aneurysm in a 28-year-old female treated with excision and primary repair. A 28-year-old female initially presents with an incidentally found pulsatile mass in her left arm. She was asymptomatic and incidentally noticed a lump which was found to be the aneurysm on further imaging workup. There was no other abnormal pulsatility noticed concerning aneurysms of other sites i.e., femoral, popliteal, abdominal, contra brachial. She denies history of trauma to the area, injection and denied family history of connective tissue disorder. Further workup including duplex ultrasound and MRA confirmed a true brachial artery aneurysm without evidence of aneurysms in the remainder of the body. The aneurysm was treated with surgical excision and primary repair with pathology negative for any connective tissue disorder. Post-operatively, the patient recovered well and was discharged on post-op day 2. Pathology report was negative for any connective tissue abnormalities. Genetic testing without causative factors. On follow-up, the patient has been doing well on an aspirin with palpable distal pulses. True brachial artery aneurysms are estimated to have an incidence of 0.17% 5 and represent an exceedingly uncommon cause of limb threatening sequelae if not treated. Those identified should undergo thorough investigation including genetic testing and imaging for other aneurysms. Surgical excision and repair with or without a conduit (autogenous or prosthetic) remain the gold standard of treatment with documented good outcomes.