HETEROZYGOUS C3 DEFICIENCY ASSOCIATED WITH A SYSTEMIC LUPUS ERYTHEMATOSUS-LIKE DISEASE

We report an 18 year old Caucasian male with an SLE-llke syndrome and decreased serum C3 in the patient and 3 relatives. Submucosal and cutaneous hemorrhage began at age 11. An erythematous rash, arthralgias, proteinuria (512-815 mg/24 hours) and thrombocytopenia (25-38,000/mm3) were detected at age 18. Serum C3, (normal 164 ± 83 mg/dL ± 2 S.D.) averaged 43 mgm/dL (range 30-60) in the propositus, 33-72 mg/dL in the mother, 69-92 mg/dL in maternal uncle and 56 mg/dL in a first cousin. Total hemolytic complement was decreased only in propositus. Specific hemolytic complement was below normal range (1950-2700 units/ml) only in family members with low protein C3: 1180 - propositus, 1770 - mother, 1560 - uncle and 1800 - cousin. Protein concentrations of Clq, C4, Factor B, properdin and specific functional C1, C4 and C2 were normal in propositus and the 11 family members. Clq precipitins, LE cells, antinuclear antibody, rheumatoid factor, C3 activating factor and cryoglobulins were absent in propositus. Skin biopsy showed vasculitis with igG, C3 and C4 deposition in dermal-epidermal junction. Prednisone therapy for thrombocytopenia resulted in a transient elevation of C3. This is the first report of an associated SLE-like disease in a probable heterozygous C3-deficient individual and differs from the cutaneous vasculltis-hypocomplementemia syndrome because of 1) the absence of Clq precipitin, 2) normal early C components and 3) the familial partial C3 deficiency.