[amelia] More variables in data subset

Dear Amelia users and creators, I am using Amelia to multiply impute missing data in a data set. In this data set, more variables are assessed for cases than for the controls. There exists a strong correlation between this additional data and the missing values that I would like to impute. Should I incorporate these additional variables in Amelia, even if none of the controls have an existing value for these variables? It is not my intention to include these additional variables in any further statistical analyses, I just want to use this additional data to make a better estimation of the missing values. Thanks in advance, Roel Mocking