Malignancies (lung cancer, breast cancer, leukemia, lymphomas) and autoimmune and/or chronic inflammatory diseases (e.g., lupus erythematosus, psoriasis, atopic dermatitis, vitiligo, alopecia areata, rheumatoid arthritis) diseases in case of STAT3 hyper-activation; hyper-IgE syndrome and chronic bacterial or mycological infections in case of STAT3 deficit. The gene discussed is STAT3; the disease is lymphoma.