Loss of leucocyte common antigen (CD45) on atypical lymphocytes in the localized but not disseminated type of Pagetoid reticulosis

Summary Atypical intraepidermal T cells in Pagetoid reticulosis did not express CD45RO, the low molecular isoform of CD45. These cells did express other CD45 isoforms in the disseminated aggressive variant (Ketron‐Goodman type). The complete CD45 family was lost from the cell surface in the henign localized variant (Woringer‐Kolopp type). Because the presence of CD4S is crucial for the function of the lymphocyte‐specific tyrosine kinase p56 lck , which is associated with lymphocyte growth and transformation, this may be the molecular basis for the non‐aggressive nature of this clonal T‐cell proliferation.