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Glossary
- 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.=
In 1994, Ranum et al.1 reported that an autosomal dominant disorder, type 5 spinocerebellar ataxia (SCA5) (OMIM 600224), occurred in 56 of 170 examined descendants of President Abraham Lincoln’s paternal grandparents.
Ranum’s group1,2 hypothesized that Lincoln may himself have had SCA5 because 1) he had a 25% “prior probability” of inheriting the disease-causing gene variant from a grandparent; 2) his age at death, 56, was within the range of disease onset seen in the kindred; 3) his gait was unusual and, according to one eyewitness, “shambling”; and, contradictorily, 4) “if President Lincoln had inherited the ataxia gene, his symptoms could have been very mild or as yet undeveloped at the time of his death.”1
Because the gene causing SCA5 has been identified,2 DNA testing could definitively diagnose Lincoln. Ranum has declared intent to “pursue a DNA test if the opportunity arose.”3 Others support this.4
Arguably, however, DNA testing is justified only when a detailed review of Lincoln’s phenotype establishes a sufficiently high probability of having SCA5. Because no such review has been performed, I herein assess the probability that Lincoln had SCA5, based on a recent compilation of primary source materials describing the physical status of Lincoln and his first-degree relatives.5,6
SCA5 IN THE LINCOLN KINDRED
Two of Lincoln’s paternal relatives—his uncle Josiah and his aunt Mary—have descendants with SCA5 (figure 1). In this kindred, initial symptoms of SCA5—gait disturbance, dyscoordinated upper limbs, and slurred speech—have appeared from ages 10 to 68, but typically from 20 to 40.1
Figure 1 Lincoln family tree
President Abraham Lincoln is in generation III. His grandfather was “Captain” Abraham Lincoln, in generation I. Ranum et al.1 supply, for generations V and later, the number of descendants of Josiah and Mary with SCA5. Question marks indicate unknown SCA5 status. An asterisk …
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Disputes & Debates: Rapid online correspondence
- SCA5 or Lincoln Ataxia?
- Abraham Lincoln may have had SCA Type 5
- Abraham Lincoln did not have type 5 spinocerebellar ataxia
- Reply from the author
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