Zhen Quan's younger brother, born in the 11th year of Datong of the Southern Liang Dynasty (545), died during the Zhenguan period of the Tang Dynasty (627-649). During the Wude period of the Tang Dynasty (618-626), he was promoted to Taichang Cheng and, along with his brother Zhen Quan, was renowned for his medical skills at the time. Liyan was skilled in medicine, proficient in materia medica, and adept at treating Chinese Taxillus Herb worm disease. He authored Materia Medica Phonetics and Meanings in seven volumes, Materia Medica Medicinal Properties in three volumes, Materia Medica Collection Records in two volumes, and Gujin Luyanfang in fifty volumes, all of which have been lost, though some fragments can still be found in Qianjin Yaofang and Waitai Miyao. His Gujin Luyanfang, as cited in Waitai Miyao, mentions "consumptive thirst with sweet urine," which is the earliest recorded description of a condition resembling diabetes in China.