Mycosis fungoides with marked hyperpigmentation.

Pigmentary changes in mycosis fungoides are not rare. Although poikiloderma and hypopigmented skin lesions have often been reported in the literature, there are few cases of mycosis fungoides presenting as a hyperpigmented skin lesion. We present a 57-year-old Japanese male with mycosis fungoides whose skin lesions showed marked hyperpigmentation. The skin lesion initially appeared as an irregularly shaped itchy annular erythema with central pigmentation predominantly on his extremities. During our 5-year follow-up, these skin lesions gradually increased in size and number. The erythema extended peripherally and became elevated with marked hyperpigmentation. Histology revealed extreme elongation of the rete ridges with infiltration of atypical large lymphoid cells characteristic of mycosis fungoides and numerous melanin granules in both the epidermal melanocytes and dermal melanophages. Although the exact mechanism of the marked hyperpigmentation is one of the unique characteristics in mycosis fungoides, especially in non-white individuals.