(WVIT) The two brothers have come to be known as the “solar kids” and their case has completely mystified Pakistani doctors.

Ages 9 and 13, the boys are normal active children during the day. But once the sun goes down, they both lapse into a vegetative state — unable to move or talk. Javed Akram, a professor of medicine at the Pakistan Institute of Medical Sciences, told The Associated Press on Thursday that he had no idea what was causing the symptoms.

“We took this case as a challenge. Our doctors are doing medical tests to determine why these kids remain active in the day but cannot open their eyes, why they cannot talk or eat when sun goes down,” he said, as he visited the pair at his hospital.

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