Infantile case of early manifestation of SLE-like symptoms in complete C1q deficiency.

C1q deficiency is a rare complement deficiency in the early part of the complement cascade. Patients with C1q deficiency have severe recurring life-threatening infections and systemic lupus erythematosus (SLE)-like symptoms. We report on a boy with recurrent life-threatening infections and SLE-like recurrent skin conditions before 2 years of age. Immunological studies revealed an undetectable level of C1q. No abnormality was observed in the urine, but renal biopsy showed segmental granulonephritis. However, the changes observed were atypical for SLE nephritis. This case of C1q deficiency was unusual because the SLE-like symptoms appeared earlier than that normally seen in complement deficiency. Therefore, this case provides insights into the development of autoimmune disease, particularly in the early phase of component deficiency, and in managing renal disease that may develop in the future. (J Nippon Med Sch 2011; 78: 322-328)