Abstract: We report a case of linear porokeratosis(LP).Genetic testing showed that the patient had a heterozygous mutation of c.683G>A(NM_002461)in the MVD gene,and his brother carried the same heter-ozygous mutation but did not have clinical phenotype.The phenomenon mainly arised from the fact that LP is a Mosaic disease which a postnatal somatic second-hit is a key factor in pathogenesis.