William of Ockham was a 13th century theologian and philosopher who espoused the medieval rule of economy, "plurality should not be assumed without necessity."1 This maxim has become known as "Ockham's razor." In the practice of medicine this principle has been taught to generations of medical students and house staff in the form of "all clinical signs, symptoms and laboratory abnormalities should be attributable to a single disease process." The physician who postulates more than one pathologic entity to account for a clinical symptom complex is treading on thin ice. Nevertheless, like all rules in medicine, Ockham's razor is not inviolate. Many patients do have more than one acute illness, and recognizing this may present a difficult challenge to the physician's clinical acumen.
In patients with multiple problems, a clear-cut relationship between disease processes is often evident, such as with a patient with acute myelogenous leukemia in whom gram-negative
Simon GL, Rios JC. Ockham's Razor Revisited. Arch Intern Med. 1984;144(7):1371-1372. doi:10.1001/archinte.1984.00350190055009