Doctor Nilrem was a male Malcorian physician on Malcor III in the 24th century. In 2367, he worked at the Sikla Medical Facility.
He was working when Rivas Jakara was admitted from injuries in a riot. He inspected him and found he was really an alien, Commander William T. Riker, who was disguised as a Malcorian. When he discovered physical differences between Riker and Malcorian physical aspects, he suggested contacting Central Security, but waited until staff could check out his story. Eventually, he informed Minister of Security Krola as well as the other staff, causing a bit of an anxious situation.
Later, when Dr. Berel refused to wake Riker, in fear of killing him, Krola had him relieved and made Nilrem the acting director. Nilrem followed the order to wake Riker. (TNG: "First Contact")