[Epidemiology and etiological factors in giant cell arteritis (Horton's disease and Takayasu's disease)]

Temporal arteritis is without a doubt the most frequent vasculitis. Incidence is age related and most patients are over 50. The incidence in Caucasian populations shows a North-South gradient with a clear predominance in northern Europe and in the northern part of the United States. In these populations, annual incidence is estimated at 15 to 30/100,000 persons over 50 years of age. The sex ratio (F/M) ranges from 2 to 4. Data in France, Scotland, Italy and Israel show an annual incidence below 10/100,000 inhabitants. The disease is very uncommon in persons of African or Asian ethnic origin. Histology and immunohistochemistry studies of the temporal artery walls favor a vasculitis triggered by one or more unknown antigens, but the cause of temporal arteritis remains unknown. A link with HLA DR4 was demonstrated early. The epidemiology of Takayasu's disease is less well known except for the very strong female predominance (90% of cases). The disease is frequent in Japan, Asia, India and South America, more uncommon in Europe and North America. The "gradient" is thus inverted compared with temporal arteritis. In Japan, among 300,000 autopsies, only 0.03% cases of Takayasu disease have been observed. The incidence of the disease in one study was 2.6 cases per million inhabitants per year. Unlike temporal arteritis, most cases begin early in the 10 to 30 year age range. Genetic susceptibility linked to HLA BW52 is observed in Asia while in the United States, it would appear, though on small numbers of cases, that the frequencies of MB3 and DR4 are increased. We emphasize the epidemiological relationship with tuberculosis and Takayasu disease.