Pseudolymphoma with mycosis fungoides manifestations, hyperresponsiveness to diphenylhydantoin, and lymphocyte disregulation.

Three patients receiving diphenylhydantoin (DPH) were seen with a reversible process suggesting mycosis fungoides. Clinical and laboratory manifestations included generalized pruritic exfoliative erythroderma, eosinophilia, lymphadenopathy, hepatosplenomegaly, circulating Sézary cells, epidermal Pautrier's microabscesses on skin biopsy, and moderate liver dysfunction. Studies of the distribution and function of the various lymphocyte subpopulations from these patients showed: (1) an increase in the relative and absolute number of T lymphocytes (85--92%); (2) significant stimulation of lymphocyte-blastic transformation by DPH and low response to pokeweed mitogen stimulation; (3) the impaired ability of T gamma lymphocytes to suppress B-cell differentiation and immunoglobulin production. With only one exception, 15 symptom-free patients on DPH showed none of these abnormalities. The clinical manifestations and immunologic abnormalities of patients with this pseudo mycosis fungoides syndrome remitted three to four weeks after DPH administration was discontinued. The proliferation of T lymphocytes and the inhibition of the function of T gamma-suppressor lymphocytes noted in these patients may be significant to the development of other types of pseudolymphoma and to that of true lymphoma.