Researchers from Japan's Kyoto University have documented just the second case in chimpanzees of a genetic disorder similar to Down syndrome in humans.
The chimp, a captive-born 24-year-old female named Kanako, has a third copy of chromosome 22, in a condition called trisomy 22. (In humans, Down syndrome is known as trisomy 21, for a third copy of chromosome 21.)
The only such prior case in the species was observed in 1969, in a chimp that did not live to be two years old.
In humans, Down syndrome can be typified by slowed growth, intellectual challenges of varying degrees and features such as crossed eyes.
Kanako, who lives at the university's Kumamoto Sanctuary, has been blind since the age of seven, following cataracts that first appeared when she was only one year old. She also has crossed eyes, thinning corneas, a congenital heart disease and underdeveloped teeth.
Researchers only learned of Kanako's unusual condition when a routine exam three years ago showed she had a heart defect. When she was found to have a "hole" in the wall between the chambers of her heart, a chromosome analysis later revealed her trisomy 22.
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While her blindness makes it tricky, and possibly unsafe, to socialize with other chimps, Kanako has made a female friend named Roman that she is allowed to see periodically. Thus far, the researchers say, the two animals get along great.