DEFICIENCY OF THE 4TH COMPONENT OF COMPLEMENT (C4) - A FAMILY CASE

In this report, an apparently healthy 38-year-old woman with a remarke dably low serum C4 value is described together with other family membe rs who had moderately low serum C4. Plasma C4 typing disclosed that th e proband inherited two C4B ''null'' haplotypes. In addition, Southern blot analysis of the C4 gene indicated that the C4A gene was partiall y deleted on one of these two haplotypes in the proband. We thus concl uded that a de novo deletion on the inherited half-null haplotype was the likeliest cause of the low C4 level.