Congenital haemophilia A is not associated with arterial aneurysms. Although the exact incidence of these lesions is unknown, they are extremely dangerous, especially in haemophilic patients, as their rupture leads to an emergency situation of fatal arterial bleeding. History of arterial trauma is the usual cause for pseudoaneurysms, whereas true aneurysms exist without previous trauma and therefore are more difficult to be diagnosed. We present the case of a radial aneurysm in a patient with mild haemophilia A that underwent uneventful surgical resection. Histological examination confirmed the diagnosis of a true radial artery aneurysm which is the first in the literature in these patient population, to our knowledge.In summary, our case concerns a 45-year-old man had been diagnosed with mild haemophilia A (FVIIIc ¼ 15 IU mL )1 ) at the age of 20 due to postoperative bleeding after appendicectomy. For that bleeding episode he was given fresh frozen plasma and on follow-up he was found to have a good response to desmopressin (DDAVP) -2 h after the subcutaneous injection of 0.3 lg kg )1 bodyweight (bw) of DDAVP the FVIIIc level increased to 55 IU mL )1 . Thus, the s.c. injection of DDAVP was the standard treatment for the mild to moderate bleeding episodes after trauma. Since 2004, when the diagnosis of arterial hypertension was made, for one bleeding episode in 2005 recombinant FVIII concentrates (rFVIII) were given to treat a severe haematoma of the left thigh, after trauma. The patient has not been infected with the hepatitis B, C or HIV virus, and no inhibitor to FVIII has been identified.Since his last visit, 3 months before, he had no complaints concerning his hand. At that time he first noticed a small painless mass in his hand without erythema and he thought that it was a ganglion. The patient had no history of penetrating or mechanical trauma. At presentation the patient showed a painful palpable mass of his right wrist with strong arterial pulses. The mass was 2 · 3 cm in size, it could be pushed, giving the impression of emptying, and after pressure removal it reappeared again. Manual finger occlusion of his radial artery at the wrist stopped the pulsation of the mass. Because of clinical suspicion of an arterial aneurysm, the patient was referred to the division of Vascular Surgery. The clinical diagnosis was then confirmed by an angiogram through the branchial artery, after the bolus administration of 20 units kg )1 bw of rFVIII. Surgical excision of the aneurysm was then planned. Preoperatively, he was given 30 units kg )1 bw of rFVIII and FVIIIc level increased to 87 IU mL )1 . Under general anaesthesia, the proximal to the aneurysm radial artery was free dissected, as well as, the distal to the aneurysm finger arteries (for the first and second finger). The aneurysm was excised (Figs 1a and 1b), the artery of the first finger was ligated and the artery of the second finger was anastomosed to the radial artery. rFVIII (20 units kg )1 bw) was repeated at 12, 24, 36 and 48 h and then once daily for an...