CTLA4 and Autoimmunity: Both LRBA hemizygous AAD patients carry the common AAD CTLA4 risk allele, in either the homozygous or heterozygous state, and given that the postulated CTLA4 risk allele effect is related to gene expression levels (7) it is possible that the loss of a copy of LRBA would compound the CTLA4-based autoimmunity risk.