Bone marrow transplantation from a human leukocyte antigen-mismatched unrelated donor in a case with C1q deficiency associated with refractory systemic lupus erythematosus.

Human C1q deficiency is frequently associated with systemic lupus erythematosus (SLE), which requires long-term systemic corticosteroid administration. We report the case of a 12-year-old female patient with C1q deficiency presenting with intractable SLE who successfully underwent bone marrow transplantation from a human leukocyte antigen (HLA)-mismatched unrelated donor with an immunosuppressive conditioning regimen based on fludarabine, melphalan, and anti-thymocyte globulin. She developed Grade I graft-versus-host disease, but did not have any transplantation-related morbidity. Complete donor chimerism has been maintained for 2 years after transplantation, leading to the restoration of C1q levels and the resolution of SLE symptoms. Normal C1q mRNA expression was observed in CD14 + cells. Hematopoietic stem cell transplantation from an HLA-mismatched donor is a feasible treatment for patients with C1q deficiency with refractory SLE that is dependent on systemic corticosteroid treatment who do not have an HLA-matched donor.