IN CONTRAST to the X chromosome, little is known about the autosomal loci for various genetic traits. Recently Gerald et al1 and Bloom et al2 have presented suggestive evidence that the controlling formation of locus the α-chain of haptoglobin is situated on one end of a No. 13 chromosome. We have studied two patients with chromosome defects and dysgammaglobulinemia. One had a No. 18 ring chromosome, which is formed by breakage in both arms with reunion of the broken ends and loss of a variable amount of material distal to each break. The other had a partial deletion of the long arm of the same chromosome. In both patients IgA was not detectable, and, in one, the level of IgG was very low. These patients are the first recognized examples of dysgammaglobulinemia associated with a chromosomal deletion.
Report of Cases
Case 1.—A 3-year-old white boy was first admitted to