When we compose medical school curricula, we choose what to stress to our students based on how common or how instructive the disease is. What are the common plagues of our society? Vascular disease, trauma, and some infectious diseases affect a large percentage of our population and rightfully assume an important place at the curriculum table. However, most diseases affect < 1% of the population. Based on what their pathophysiologic, mechanistic, or basic science processes can teach us, these uncommon diseases assume a role in our curriculum that is greater then their frequency would seem to warrant. Many genetic diseases and cancers fall into this category. Other diseases such as rabies or necrotizing fasciitis are so terrible that even though most physicians never treat a single case, we teach students about them and test for knowledge of these illnesses on national board and specialty examinations. But would we not be remiss if there was an illness that affected a large number of our patients and, if this illness caused disability and death in a majority of the patients it affected, we failed to teach about this illness? What if the haystack was full of needles, but we failed to even recognize the haystack?