A 35-year-old woman from rural India presents with progressive dyspnea, chest pain, and signs of aortic regurgitation. Angiography shows narrowing of the aorta and its major branches with a 'skip lesion' pattern. Which is the most common site of initial vascular involvement in this condition?

Explanation

## Takayasu Arteritis: Pattern of Vascular Involvement **Key Point:** Takayasu arteritis (TA) is a large-vessel vasculitis that predominantly affects the aorta and its proximal branches. The aortic arch and its immediate branches (subclavian, common carotid, and vertebral arteries) are the **most commonly and characteristically involved** sites. ### Epidemiology & Demographics - Predominantly affects young women (female:male = 8:1) - Most common in Asia, particularly India, Japan, and Southeast Asia - Peak incidence: 15–30 years of age ### Pattern of Vascular Involvement | Aortic Region | Frequency | Clinical Features | |---|---|---| | **Aortic arch & proximal branches** | **~60–70%** | **Most common; arm claudication, absent pulses** | | Ascending aorta/aortic root | ~30% | Aortic regurgitation, aortic root dilation | | Descending thoracic aorta | ~40% | Often concurrent with arch involvement | | Abdominal aorta | ~30% | Renal artery stenosis → hypertension | | Pulmonary arteries | ~10–15% | Pulmonary hypertension | | Coronary arteries | ~10% | Myocardial ischemia, MI | **High-Yield:** The **aortic arch and its proximal branches (subclavian, carotid, vertebral)** are the most frequently affected sites, occurring in 60–70% of cases. This is the hallmark distribution that distinguishes TA from other large-vessel vasculitides. ### Pathological Features - Granulomatous inflammation of the media and adventitia - Giant cells and epithelioid histiocytes (similar to GCA) - Intimal proliferation and fibrosis → stenosis and narrowing - **Skip lesions** = alternating areas of involvement and normal vessel (pathognomonic) ### Clinical Manifestations by Site **Aortic arch involvement:** - **Pulseless disease** = absent pulses in upper extremities - Arm claudication and blood pressure differential between arms - Subclavian steal syndrome - Carotid involvement → dizziness, syncope **Ascending aorta/aortic root:** - Aortic regurgitation (most common cardiac complication) - Aortic root dilation - Heart failure **Abdominal aorta/renal arteries:** - Hypertension (from renal artery stenosis) - Mesenteric ischemia (rare) **Pulmonary arteries:** - Pulmonary hypertension - Right heart failure **Clinical Pearl:** The combination of **young woman + aortic arch stenosis + aortic regurgitation + skip lesions on angiography** is virtually pathognomonic for Takayasu arteritis. The "pulseless disease" phenotype (absent upper extremity pulses) is a classic presentation. **Mnemonic: TAKAYASU** — **T**horacic aorta, **A**ortic arch, **K**ey branches (subclavian/carotid), **A**bdominal aorta (less common), **Y**oung women, **A**sia, **S**tenosis/Skip lesions, **U**pper extremity claudication. **Warning:** Do not confuse with Giant Cell Arteritis (GCA), which affects **extracranial branches of the carotid system** (temporal artery) and occurs in elderly patients (>50 years). TA is a disease of young women; GCA is a disease of elderly.