Fever of undetermined origin: not what it used to be.

Eighty cases of fever of undetermined origin seen at Dallas VAMC from 1979 to 1985 were analyzed. Infectious etiology was the cause in one half, with equal numbers of localized infections or systemic infections. In contrast to older series, viral infections were frequently seen, but tuberculosis and malaria were less commonly noted. Solid tumors were the most frequently diagnosed non-infectious cause of fever. Fevers secondary to malignancy commonly responded to non-steroidal anti-inflammatory agents. Patterns of illness were helpful in defining certain diseases such as adult Still's disease and polymyalgia rheumatica. Diagnostic tests of value are discussed.