Marked Different Responses of rhIGF-1 and Steroid Therapy in Two Patients with Type B Insulin Resistance Complicated by Systemic Lupus Erythematosus

インスリン受容体異常症B型は，抗インスリン受容体抗体の異常産生により著明なインスリン抵抗性を呈する稀な疾患であり，SLEなどの自己免疫疾患を高頻度に合併する．経験した2例の臨床的特徴と治療効果を比較した．症例1は50歳，女性．SLEの診断時にPG 220 mg/dl, IRI 830 μU/ml, HbA1c 8.0%, 抗インスリン受容体抗体陽性より本症の合併が診断された．血糖コントロールにrhIGF-1（10 mg/日）投与が著効した．SLE診断時から開始したステロイド療法によって，SLEと本症は平行して寛解した．症例2は59歳，男性．SLEの診断時にPG 67 mg/dl, IRI 316 μU/ml, HbA1c 9.5%, 抗インスリン受容体抗体陽性より本症の合併が診断された．血糖コントロールにrhIGF-1は無効であった．さらにステロイド療法で両疾患の活動性は軽快せず，むしろ血糖値は悪化した．しかし，免疫抑制剤（シクロホスファミド，シクロスポリンA）の投与によってSLEの活動性低下と共に本症も軽快した．本2症例は，SLEを合併した点では類似するものの治療の反応性が著しく異なった．インスリン受容体異常症B型の治療を考える上で，抗インスリン受容体抗体のclonalityと基礎疾患の活動性の違いによる免疫抑制療法に対する反応の違いを考慮することが重要と考えられた．Type B insulin resistance syndrome is an autoimmune disease caused by anti-insulin receptor autoantibodies and is frequently accompanied by other autoimmune disorders. The choice of treatment modality may thus be difficult in these patients. We report two patients with type B insulin resistance syndrome associated with systemic lupus erythematosus (SLE), whose responses to therapeutic agents differed markedly. Case 1: A 50-year-old Japanese woman with a SLE activity index (SLEDAI) score of 10 had her hyperglycemia treated successfully with recombinant human IGF-1 (rhIGF-1) (10 mg/day), but not even high dose of insulin were effective. Anti-insulin receptor autoantibodies and SLE activity may be dramatically decreased by SLE therapy with prednisolone (30 mg/day). Case 2: In contrast, a 59 year-old Japanese man with a SLEDAI score of 26 had hyperglycemia resistant to IGF-1 therapy, as were anti-insulin receptor autoantibodies and SLE activities to prednisolone. Only intensive immunosuppressive therapy with cyclophosphamide and cyclosporine A was effective in reducing SLE activity, high plasma glucose, and anti-insulin receptor autoantibody titers. The clinical courses of these two patients are highly indicative of differences considering the choice of therapeutic modalities for type B insulin resistance syndrome associated with other autoimmune diseases