Focal contact sensitivity to nitrogen mustard in lesions of cutaneous T-cell lymphoma (mycosis fungoides).

A report is presented on a patient with mycosis fungoides who developed a remarkable focal contact sensitivity to topically applied nitrogen mustard in aqueous solution (1/5000). Although the nitrogen mustard was applied over the entire skin surface, repeated challenge demonstrated that the eczematous contact dermatitis reaction was limited precisely to the areas of clinically identifiable mycosis fungoides. The surrounding normal skin showed no response. The basis for the surprising focal induction and localization of contact dermatitis is not known but might reflect the presence of a clone of malignant T-lymphocytes which became specifically sensitized to the nitrogen mustard.