Macrocephaly

Already Mexico City is a warning to other developing countries where centralized government, a high birth rate, neglect of agriculture and the rush to industrialize have combined to encourage migration to the cities. Twenty percent of the country's population lives here, and the term urban macrocephaly has been coined to describe the phenomenon.

Source: wiktionary

Another physical impact of urbanization in Asia has been the intensification of the primacy of capital cities. Most countries in the region—except China, Vietnam, and India—are well known for suffering from “macrocephaly disease.” Capital cities such as Tokyo, Taipei, Seoul, Jakarta, Manila, and Bangkok have a population that is more than double that of the next largest metropolitan area.

Source: wiktionary