Familial persistent polyclonal B-cell lymphocytosis.

We report the occurrence of the syndrome of persistent polyclonal B-cell lymphocytosis in a brother and a sister. Both showed the morphological and immunophenotypic features of this rare disorder. In addition both had mild splenomegaly, increase of serum IgM and serological evidence of previous EBV infection. Of interest, two additional brothers had no evidence of PPBL but were indistinguishable in terms of HLA haplotype (HLA-DR7), smoking habits or evidence of EBV infection. These observations provide additional support for a genetic basis of the syndrome but suggest that pathogenic factors other than those known so far may be required for its full expression.