Rule - Every common disease was, at some point, a rare disease.
Brief Rationale - Every epidemic begins with a solitary case. Common diseases are equivalent to epidemics that settle in to stay.
Of course, this phenomenon of rare diseases becoming common diseases is something that happens all the time with infectious diseases. In a sense, we see this every year when a new strain of flu virus emerges as an epidemic. In a prior blog, we looked at several specific examples wherein environmental, and sociological factors played a role in transformaing a rare disease into a common disease. Specifically:
Heart disease. Increased availability of cheap fatty and sweet foods, combined with social factors that favor a sedentary life-style, raised the heart attack from a collection of rare, hereditary conditions to one of the most common causes of death in industrialized societies.
Colon cancer. Common in the United States, colon cancer has an incidence of 40/100,000. In Africa and some parts of Asia, colon cancer is a rare disease, with an incidence under 5/100,000 (2). Speculation abounds to explain why this is so, but the the issue of diet looms large. The low-fiber, low-vegetable, high-meat diet preferred in high-incidence societies, contrasted with the high-fiber, high-vegetable, low-meat diet in the low incidence societies provides a credible, if unproven, explanation.
AIDS. Late in 1981, a Haitian man presented at Jackson Memorial Hospital in Miami with a constellation of infectious diseases, a strange rash, and mouth lesions of an unfamiliar type. At the time, the attending physicians were baffled. Eventually, after a desperate review of the newest literature, a diagnosis of an extremely rare diseases tentatively named GRIDS (gay-related immune disease syndrome), was rendered. Today, GRIDS, now known as AIDS, is a diagnosis that can be rendered, without hesitation or error, by a first-year medical student. In 1981, there were about a dozen well-document cases in the U.S. In 2011, 1.7 million people died of AIDS worldwide (3).
Lung cancer. Prior to the popularization of cigarette smoking, lung cancer was extremely rare. Today, lung cancer is the leading cause of cancer deaths in every country where smoking is common.
Today, let's look at an inherited genetic condition that has morphed from a single case to a common disease, all within a half century.
There is an inherited immunodeficiency of cattle caused by a deficiency of leukocyte adhesion factor. Affected cattle are homozygous for a gene allele that codes for a substitution in a a single amino acid in its protein product. Heterozygotes (i.e., cattle with an unpaired mutant allele) are common in the U.S., with a carrier rate of about 10%. Every cattle with a mutant allele is a descendant from one bull, whose sperm was used to artificially inseminate cows in the 1950s and 1960s (1). A disease that was essentially non-existent in 1950 became a common scourge of the dairy industry within a half-century, all due to the founder effect amplified by modern animal husbandry
Rare Disease Day is coming up February 29 (a rare day for rare diseases). In honor of the upcoming event, I'll be posting blogs all month, related to the rare diseases and to rare disease funding.
- Jules Berman (copyrighted material)
key words: rare disease, orphan drugs, orphan diseases, zebra diseases, rare disease day, disease complexity, common diseases, jules j berman
 Kehrli ME, Ackermann MR, Shuster DE, van der Maaten MJ, Schmalstieg FC, Anderson DC, et al. Bovine leukocyte adhesion deficiency: beta(2) integrin deficiency in young Holstein cattle. Am J Path 140:1489-1492, 1992.
 World Cancer Research Fund and American Institute for Cancer Research Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective. Washington, DC, American Institute for Cancer Research, 2007. Available at: http://www.aicr.org/assets/docs/pdf/reports/Second_Expert_Report.pdf, viewed August 13, 2015.
 Global Health Observatory. HIV/AIDS. World Health Organization. Available from http://www.who.int/gho/hiv/en/, viewed July 27, 2013.