Patients with melanoma may develop skin depigmentation spontaneously or following therapy, referred to as melanoma-associated leucoderma (MAL). As clinical presentation of MAL may precede primary/metastatic melanoma detection, recognition of MAL is important to prevent its misdiagnosis as vitiligo and the subsequent application of immunosuppressive treatment. To reveal the immunity involved in MAL development, we investigated the presence of antibody and T-cell immune responses directed against the melanocyte-differentiation-antigens MART-1 (Melan-A), tyrosinase and gp100 in patients with MAL, as compared to patients with vitiligo. Autoantibodies to gp100 and tyrosinase were commonly found in both diseases. Interestingly, MART-1 antibodies were only present in patients with MAL. Melanocyte antigen-specific T cells were found in all patients, with relatively more specific T cells in patients with active vitiligo. Although MAL and vitiligo may appear clinically similar, our results indicate that the humoral immune responses against MART-1 differ between these diseases, which can help to differentiate MAL from vitiligo.

The immune responses found in this patient, probably enhanced by radiotherapy, are thought to have contributed to his favourable clinical course. Radiotherapy may act as local immunotherapy in patients with melanoma by destroying melanocytes, leading to the induction, or enhancement, of already existent antimelanoma immunity. As in patients treated with immunotherapy, this may lead to MAL, also at distant sites from the treated area. This patient is a clear example of the positive prognostic value of MAL, which is possibly induced by radiotherapy, for patients with melanoma.

Monobenzone is a 4‐substituted phenol that can induce vitiligo and antimelanoma immunity. We investigated the influence of the chemical structure on the biological activity of a series of structurally related 4‐substituted phenols. All phenols inhibited cellular melanin synthesis, and eight of ten phenols inhibited tyrosinase activity, using the MBTH assay. These phenols also induced glutathione (GSH) depletion, indicative of quinone formation and protein thiol binding, which can increase the immunogenicity of melanosomal proteins. Specific T‐cell activation was found upon stimulation with phenol‐exposed pigmented cells, which also reacted with unexposed cells. In contrast, 4‐tertbutylphenol induced immune activation was not restricted to pigment cells, analogous to contact sensitization. We conclude that 4‐substituted phenols can induce specific T‐cell responses against melanocytes and melanoma cells, also acting at distant, unexposed body sites, and may confer a risk of chemical vitiligo. Conversely, these phenols may be applicable to induce specific antimelanoma immunity.