Drug dosage may also influence morbidity, with studies showing a higher risk of PAI at doses of ibritumomab above 5 mg/kg (26).This is similar to traditional Addison’s disease, resulting from adrenocortical destruction mediated by T cells, etc. ICI may break tolerance to adrenal autoantigens (e.g.,21-hydroxylase), involving susceptibility genes (e.g. CTLA-4, PDCD1) and specific HLA haplotypes (e.g., HLA-DR3-DQ2) (27, 28). Here, CTLA4 is linked to primary adrenal insufficiency.