The rare diseases that include more single gene disorders like Duchenne muscular dystrophy, Huntington diseases. these diseases occur many of the childhood and the adults disease and Crohn’s disease and some of the childhood cancers are infectious diseases. The rare disease is like a health condition of very low persons that effects a unique number of people compared with other diseases in general population. The causes of the rare diseases are such as diet, smoking, environmental factors or exposure to the chemicals, these also play an important role in rare diseases. that factors may have directly causes diseases or with the genetic factors are also cause or increase the factors of diseases. These types of diseases are called as rare, genetic disease or disorder.