- Molecular characterization of properdin deficiency type III: dysfunction produced by a single point mutation in exon 9 of the structural gene causing a tyrosine to aspartic acid interchange. Fredrikson, G.N., Westberg, J., Kuijper, E.J., Tijssen, C.C., Sjöholm, A.G., Uhlén, M., Truedsson, L. J. Immunol. (1996)