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Parapsoriasis has been described rarely in childhood; a few reports mention this condition as preceding early mycosis fungoides. We report a boy age 15 and a girl age 8 years with different clinical features of parapsoriasis who were followed clinically and histologically for about four years. Immunophenotyping of the skin infiltrate and a T cell receptor gene rearrangement analysis were performed on each. The infiltrate was composed mainly of CD4+ and CD45+ lymphocytes in the first patient and of CD8+ and CD45+ in the second. No T cell receptor gene rearrangements were found. The paucity of knowledge about the evolution of this entity in childhood and its relationship to mycosis fungoides makes follow-up critical. The importance of immunophenotyping and immunogenotyping is particularly stressed.

A monoclonal antibody OKT 9 which detects a determinant expressed by a variety of proliferating cell types has been recently developed. This antibody was used in conjunction with the immunoperoxidase technique to study the cutaneous lymphoid infiltrates of nine patients with mycosis fungoides, one patient with lymphomatoid papulosis, two patients with Sézary syndrome, and ten patients with large plaque atrophic parapsoriasis (a condition which may terminate in overt mycosis fungoides.) OKT 9 reactive cells were identified in all cases of mycosis fungoides examined, in one case of lymphomatoid papulosis, one of two cases of Sézary syndrome, and one of ten cases of large plaque atrophic parapsoriasis. These results suggest that further studies using OKT 9 should be performed to assess whether OKT 9 reactivity may be used as a prognostic marker in cutaneous lymphomas and prelymphomas.

Tissues from atrophic large plaque parapsoriasis were examined using the indirect immunoperoxidase technique with a monoclonal T cell antibody as primary antibody, and affinity isolated peroxidase conjugated goat anti-mouse IgG as second stage antibody. The "T" cell nature of the dermal infiltrate and of single exocytic epidermal lymphocytes was demonstrated. The results obtained suggest that the method utilized will be useful for the demonstration of lymphoid cell subpopulations in a variety of cutaneous disorders in which a lymphocytic infiltrate forms a significant component of the histopathology observed. This technique also has the potential of providing information on the topographic localization and differentiation of lymphocytes within the various levels of the skin. Certain technical manipulations which may result in an improvement in the quality of results obtained are also discussed.