Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Omenn syndrome ?
    ### Response:
    What causes Omenn syndrome? Omenn syndrome is a genetically heterogeneous condition (meaning that it may be caused by a number of different genes). While most cases are attributed to mutations in the RAG genes (RAG-1 and RAG2 genes have been mapped to chromosome band 11p13), recent reports describe Omenn syndrome in the absence of RAG mutations.
    