An unusual form of persistent polyclonal B lymphocytosis in an infant

We report a case of persistent polyclonal Lymphocytosis in an infant. The c irculating lymphocytes were of a small to medium size and a small proportio n were larger and had lymphoplasmacytoid features. The presence of either a n infectious or mutagenic agent was excluded. The polyclonal B-cell nature of the lymphocyte was demonstrated by immunological markers and confirmed b y Southern blot analysis and by polymerase chain reaction targeting immunog lubulin genes. In contrast to the common form of polyclonal lymphocytosis, this case was not associated with HLA-DR7 and/or abnormalities of chromosom e 3, p53 or Bcl2/IgH. Whether this lymphocytosis represents a premalignant or a benign condition remains uncertain, although there has been no progres sion to date.