title: Atypical hypocomplementemic vasculitis syndrome in a child.
abstract: We report a patient who developed recurrent urticaria and angioedema at age 2 years, severe hypocomplementemic glomerulonephritis at 11 years, and end-stage renal disease at 14 years. His disease resembled the hypocomplementemic vasculitis syndrome but was atypical in its early age of presentation, severe hypocomplementemia, and progression to end-stage renal disease. Serum C1q levels were extremely low, and C4, C2, C3, and C5 levels were significantly reduced. Serum C1 inhibitor (C1INH) levels were slightly low, presumably from consumption. Circulating C1INH-C1r-C1s complexes were evidenced by reduced ratios of functional to antigenic C1INH and antigenic C1r to C1s. Family members had normal functional and antigenic levels of all complement components studied. The patient's serum, erythrocytes, platelets, and mononuclear cells did not activate complement when mixed with normal target serum. Absence of a circulating complement activator and the low serum C3 and C5 levels suggested the presence of a solid-phase complement activator, possibly related to renal or systemic vascular endothelium. As in patients with homozygous deficiencies of classical pathway components, a severe, prolonged, acquired C1q deficiency may have predisposed this patient to the development of glomerulonephritis.
authors.forename: F B
authors.initials: FB
authors.lastname: Waldo
authors.forename: P A
authors.initials: PA
authors.lastname: Leist
authors.forename: C F
authors.initials: CF
authors.lastname: Strife
authors.forename: J
authors.initials: J
authors.lastname: Forristal
authors.forename: C D
authors.initials: CD
authors.lastname: West
mesh_terms: D000799:Angioedema / Q000209:etiology / Q000276:immunology; D002648:Child; D003166:Complement Activating Enzymes / Q000097:blood / Q000172:deficiency / Q000378:metabolism; D003167:Complement Activation; D003172:Complement C1 / Q000378:metabolism; D003174:Complement C1 Inactivator Proteins / Q000172:deficiency / Q000378:metabolism; D015922:Complement C1q; D015923:Complement C1r; D003173:Complement C1s; D003175:Complement C2 / Q000172:deficiency; D003176:Complement C3 / Q000172:deficiency; D003181:Complement C4 / Q000172:deficiency; D003182:Complement C5 / Q000172:deficiency; D003165:Complement System Proteins / Q000172:deficiency* / Q000378:metabolism; D005921:Glomerulonephritis / Q000209:etiology / Q000276:immunology; D006801:Humans; D008297:Male; D013577:Syndrome
chemical_list: D003172:Complement C1; D003174:Complement C1 Inactivator Proteins; D003175:Complement C2; D003176:Complement C3; D003181:Complement C4; D003182:Complement C5; D015922:Complement C1q; D003165:Complement System Proteins; D003166:Complement Activating Enzymes; D015923:Complement C1r; D003173:Complement C1s