By Gary S. Hoffman, MD, MS
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Emerging evidence suggests that giant cell arteritis (GCA) and Takayasu’s arteritis (TAK) may be a continuum of the same illness. This article reviews their commonalities and differences and shares insights on this question from ongoing Cleveland Clinic research.
Giant Cell Arteritis
GCA is the most common form of vasculitis among adults older than age 50. It is most often recognized in white individuals, especially those living in northern latitudes. Incidence rates among people older than 50 years vary from 30 to 70 cases per 100,000 in Scandinavia to less than 10 per 100,000 in southern Europe and about 1 to 2 per million in Asia. GCA is highly uncommon among blacks (0.4/100,000/year). The median age in most series is about 70 to 75. There is a clear gender bias, with women affected about three to four times more often than men.
TAK is similar to GCA in many ways, yet different in others. The most obvious difference is age. The median age at TAK onset is 25 to 30. TAK has a similar but more striking gender bias, with females affected at least eight times more often than are males. While much of the TAK literature has emphasized a predilection for Asians, recent reports that reflect diverse racial and ethnic populations (e.g., in Italy, France, South Africa, Mexico, South America and the United States) have raised questions about the accuracy of this perceived predominance among Asians.
Demographic features of patients and disease manifestations between cohorts can vary considerably. In TAK cohorts in Japan, Korea, the United States, France and Italy, females account for 80 percent or more of patients, while in India females make up just over 60 percent of those affected. In Japan almost all patients are Asian; in the U.S. and Italy patients are predominantly white; and in Africa they are almost entirely black.
Comparing Clinical Profiles
Can one effectively argue that these diseases are indeed a continuum of the same illness? Most agree that the age boundaries for what is called either GCA or TAK are arbitrary. Many investigators ignore this parameter.
Both GCA and TAK involve the aorta and its primary branch vessels, with the most frequent lesions being within the thoracic aorta and its arch vessels. Imaging studies have revealed marked overlap in disease topography (Figures 1 and 2). Postmortem studies in GCA have shown histological evidence of active disease in vessels of the same caliber and distribution as in TAK, although stenoses and aneurysms are far less common in life in GCA. Both GCA and TAK are very responsive to corticosteroid therapy, and both have high rates of relapse, leading many authorities to believe that neither of these diseases is self-limiting.
Figure 1. Angiogram in a woman complaining of arm claudication. Identical findings were present bilaterally. If you were told she was 28 years old, the diagnosis would be Takayasu’s arteritis. However, she was 82 years old and had giant cell arteritis.
Figure 2. MRI revealing the dilated (aneurysmal, 5.5 cm [normal, 3.5 cm]) cross-section of the aortic root in another female patient. This inflammatory lesion occurs in about 20 to 30 percent of patients with either Takayasu’s arteritis or giant cell arteritis. In either case, there is a high risk of rupture or dissection.
Skewed Phenotypes of a Single Disease?
In our own studies comparing diseases, the same standard interview tool, examination and vascular imaging protocol were applied to all patients. While similarities were common, a greater frequency of certain findings was noted in GCA, including jaw claudication, visual loss or aberration, and scalp tenderness. Conversely, pulselessness, blood pressure asymmetry and bruits were more common in TAK.
These findings have led us to suggest that these may not be separate diseases but rather skewed phenotypes of a single disease, influenced by genetic background, age-related structural changes, immunologic senescence and environmental triggers. Definitive proof of that hypothesis is the focus of our ongoing research.
Dr. Hoffman is a member of the Department of Rheumatic and Immunologic Diseases and the Center for Vasculitis Care and Research. He is Professor of Medicine at Cleveland Clinic Lerner College of Medicine. He can be reached at 216.445.6996 or email@example.com.