Abbreviations: AD: atopic dermatitis; CyA: cyclosporin A; FceRI: high-affinity IgE receptor; HND: head and neck dermatitis; IL: interleukin; LC: Langerhans cells; MTX: methotrexate; MMF: mycophenolate mofetil; M. sympodialis: Malassezia sympodialis; SCORAD: scoring atopic dermatitis; S. aureus: Staphylococcus aureus; SIT: allergen-specific immunotherapy; T reg: regulatory T cells; TPMT: thiopurine methyltransferase. The gene discussed is TPMT; the disease is Alzheimer disease.