Abraham Lincoln did not have type 5 spinocerebellar ataxia

An autosomal dominant genetic disorder, type 5 spinocerebellar ataxia (SCA5), occurs in multiple descendants of one paternal uncle and one paternal aunt of President Abraham Lincoln. It has been suggested that Lincoln himself had the disease and that his DNA should be tested for an SCA5-conferring gene. Herein, I review the pertinent phenotypes of Lincoln, his father, and his paternal grandmother, and conclude that 1) Lincoln's father did not have SCA5, and, therefore, that Lincoln was not at special risk of the disease; 2) Lincoln had neither subclinical nor visible manifestations of SCA5; 3) little evidence suggests SCA5 is a "Lincolnian" disorder; and 4) without additional evidence, Lincoln's DNA should not be tested for SCA5.