31. Takayasu arteritis presenting as bilateral popliteal artery aneurysm: a rare presentation of a rare disease

INTRODUCTION: Takayasu arteritis (TA) is a rare, yet well recognised, chronic granulomatous arteritis that mostly affects large vessels in those below 50 years of age. According to the 2012 Chapel Hill Consensus Conference on the Nomenclature of Systemic Vasculitides, Takayasu arteritis is classified as large vessel vasculitis as it mainly affects the aorta and its major branches. However, our patient is outside the norm as he has biopsy-proven Takayasu arteritis with no or little involvement of the aorta. Instead, he presented with bilateral popliteal artery aneurysm. CASE DESCRIPTION: The patient is a healthy Yemeni gentleman. In 2011 (26-years-old), he started to complain of multiple joint pain and swelling associated with morning stiffness which was relieved after taking some medications. Incidentally, he was found to have high blood pressure which was not investigated as he was lost to follow-up. In 2016 (31-years-old), his symptoms recurred. He was diagnosed to have seronegative rheumatoid arthritis and started on csDMARDs, but he stopped them, and he was lost follow-up again. In July 2018 (33-years-old), he presented with complaints of painful swelling at the back of his right knee for around one month. The swelling was found to be a pulsatile mass and ultrasound was suggestive of popliteal artery aneurysm. CT angiography of lower limbs confirmed the presence of bilateral popliteal artery aneurysm. He underwent excision of the right aneurysm with vein interposition graft and rheumatology team was consulted. Apart from polyarthritis and hypertension, he denied any symptoms related to connective tissue diseases or vasculitides. He does not smoke. He was born to consanguineous parents but no family history of rheumatic or hereditary collagen disorders. He has normal body habitus, normal skin turgor, intact peripheral pulses and no evidence of synovitis. His laboratory workup revealed normal blood count, biochemistry panel and urinary studies but raised inflammatory markers. All serology and autoimmune workup came back negative. CT angiography of brain, chest and abdomen showed aortic ectasia with stenotic lesions in renal arteries. Biopsy of the resected aneurysm showed chronic inflammation with giant cells infiltrate compatible with TA. He was treated with steroids and intravenous cyclophosphamide pulse therapy for 6 months and then maintained on methotrexate. He is scheduled for angioplasty of the renal arteries. DISCUSSION: Despite being considered a rare disease, Takayasu arteritis has been described in many parts of the Arab world. According to a 2014 systematic review by K Mustafa, the epidemiological and clinical features of TA in Arabs were similar to different parts of the world. However, this patient is unique in several ways. He presented mainly with episodes of inflammatory polyarthritis of large and small joints which was diagnosed as rheumatoid arthritis, because he did not have the usual constitutional symptoms (fever, weight loss, fatigue, and arthralgia) that are characteristic of the inflammatory phase of TA. The only clue that could have been used to point towards vasculitis as a cause of his symptoms was the overlooked high blood pressure which affects between 33–83% of patients with TA; reflecting the common involvement of the main renal arteries in TA. Hence, the delay in the diagnosis which is also a common finding in reported cases of TA worldwide. Most angiographic studies done to show the pattern of vascular involvement in TA showed that the thoracoabdominal aorta was the most common vessel involved, followed by the subclavian vessels with some differences between Japanese and Indian populations. However, many reported cases demonstrated the involvement of medium and small size vessels as well. CT angiogram of the patient did not convince us of any aortic involvement. However, there was stenotic lesions involving the renal arteries and aneurysmal dilatation of both popliteal arteries. This pattern of involvement that spared the aorta and its major branches raised the question of other types of vasculitides such as Behçet’s disease and polyarteritis nodosa, which made us treat him with intravenous cyclophosphamide initially. However, the clinical presentation and the biopsy supported the diagnosis of Takayasu arteritis rather than other vasculitides, so we have decided to maintain the patient on methotrexate. KEY LEARNING POINTS: Patients presenting with symmetric polyarthritis should be assessed thoroughly before labelling them as rheumatoid arthritis, especially if they are seronegative in order to not miss other important differential diagnoses such as in this case the diagnosis of vasculitis. Paying attention to other associated symptoms such as dermatologic or eyes manifestations or hypertension, can help in pointing towards other important differentials. Hypertension is an important and common manifestation of the vasculitides and can be the only presenting feature to unmask the presence of vasculitides. Therefore, vasculitides should be kept in the differential diagnosis of patients with secondary hypertension. TA is a disease of the aorta and its major branches. However, it can in rare situations affect other vessels and can present without involvement of the aorta. CONFLICTS OF INTEREST: The authors have declared no conflicts of interest.