Resources that have lists of diseases in alphabetical order are the American Academy of Dermatology and the National Organization for Rare Disorders. The American Academy of Dermatology begins its list with acanthosis nigricans, a condition that causes the skin to darken, thicken and take on a velvety feel.
The list ends with vitiligo, a disorder that causes the skin and other pigmented areas of the body to lose color, according to the American Academy of Dermatology.
The first entry in the list of rare diseases in the National Organization for Rare Disorders database is Aarskog Syndrome. This disease causes stunted growth, skeletal deformities and mild mental retardation. The last entry is Zollinger Ellison Syndrome, a disease in which the patient develops a tumor that secretes large amounts of the hormone gastrin.