Leukomelanoderma Resembling Hyperpigmented Mycosis Fungoides.

Acquired circumscribed hyperpigmented patches and plaques have various differential diagnoses, including post-inflammatory hyperpigmentation and mycosis fungoides (MF). Leukomelanoderma is an uncommon cutaneous condition in which the pathogenesis is not fully elucidated. It has been reported that leukomelanoderma occurs after allergic contact dermatitis from hydroquinone or acute cutaneous graft-versus-host disease (1,2). Hyperpigmented MF is a cutaneous T-cell lymphoma with a frequent CD8+ phenotype (3). Herein, we report a case of leukomelanoderma clinically and histologically resembling hyperpigmented MF. A 55-year-old Japanese woman was referred to our department for evaluation of reticulate pigmentation with pruritic erythema on the face. She had used commercially available depigmenting cosmetic reagents for 20 years and ointment containing 10% hydroquinone for 3 months. Physical examination revealed diffuse hyperpigmentation and demarcated hypopigmented macules on the face and neck (Figure 1, a). Dermoscopy showed depigmented spots and reticulated plus dotted hyperpigmentation; it presented a pseudo-pigment network (Figure 1, b). Histological examination of a tissue specimen biopsied from the lesion showed superficial band-like lymphocytic infiltration in dermis accompanying single cells or small clusters in epidermis (Figure 1, c). Interface changes were observed together with melanophages in the dermis. Melan-A-positive melanocytes were absent. Immunohistochemical analysis demonstrated that the epidermotropic lymphocytes were CD3+CD7-, and they had predominance of CD8+ cells (Figure 1, d). These immunohistochemical results mimicked MF. However, PCR analysis of the T-cell receptor g-gene rearrangement was negative. Closed patch test result with hydroquinone (5% pet.) was graded D2 (+?) and D3 (+). Ten months after discontinuing cosmetic reagents and hydroquinone, the pigmentary changes showed improvement. The pathomechanism of leukomelanoderma is unclear. Although post-inflammatory pigmentation due to allergic or contact dermatitis together with direct depigmenting effects from hydroquinone use has been suggested (1), the immunophenotype of T-cells has not been examined. As observed in our patient, interface changes with melanophages, in addition to frequent CD8+ phenotype of the epidermotropism and dermal infiltrate of lymphocytes, were characteristic for hyperpigmented MF (3). Moreover, minimal CD7 expression was a specific finding for MF (4). T-cell receptor clonality was negative in our patient, but the clonality appears to be detected by PCR in up to 50% of the patients with early MF (3). In contrast, the closed patch test was positive for hydroquinone in our patient, and it is reported that CD8+ T-cells are recruited to the interphase between the epidermis and the dermis of the patients with allergic contact dermatitis (5). CD8+ T-cells might contribute to acute cutaneous graft-versus-host disease-like interface changes and destroy melanocytes in the leukomelanoderma lesion. Allergic contact dermatitis presenting as leukomelanoderma was thus suggested in our patient. However, further reports and studies are required to support this issue. Therefore, we considered it necessary to follow the patient, since MF was not absolutely eliminated.