Hypopigmented mycosis fungoides: a review of its clinical features and pathophysiology / Micose fungoide hipocromiante: uma revisao de seus aspectos clinicos e fisiopatologicos

Several distinct clinical forms of mycosis fungoides have been described. Hypopigmented mycosis fungoides should be regarded as a subtype of mycosis fungoides, insofar as it presents some peculiar characteristics that contrast with the clinical features of the classical form. Most patients with hypopigmented mycosis fungoides are younger than patients typically diagnosed with classical mycosis fungoides. In addition to typical dark-skinned individuals impairment, hypopigmented mycosis fungoides has also been described in Asian patients. The prognosis for hypopigmented mycosis fungoides is much better than for classical mycosis fungoides: hypopigmented mycosis fungoides is diagnosed when there are only patches of affected skin, and lesions usually will not progress beyond terminal stages, although they can persist for many years. Diagnosis should involve clinicopathologic correlation: skin biopsy analysis often reveals intense epidermotropism, characterized by haloed, large, and atypical CD8+ lymphocytes with convoluted nuclei, in contrast to mild to moderate dermal lymphocytic infiltrate. These CD8+ cells, which participate in T helper 1-mediated immune responses, prevent evolution to mycosis fungoides plaques and tumors and could be considered the main cause of the inhibition of melanogenesis. Therefore, hypopigmentation could be considered a marker of good prognosis for mycosis fungoides.

Ultimamente diferentes formas clínicas da micose fungoide têm sido descritas. A micose fungoide hipocromiante pode ser considerada um subtipo da micose fungoide, apresentando algumas características peculiares que contrastam com os achados da forma clássica da micose fungoide. A maioria dos pacientes com micose fungoide hipocromiante são mais jovens que aqueles acometidos pela micose fungoide clássica. Esta variante é descrita principalmente em indivíduos melanodérmicos (afroamericanos e asiáticos). O prognóstico é melhor que o observado para a forma clássica: ao diagnóstico, os pacientes apresentam somente "patches", que tendem a perdurar por longos períodos, sem evolução para estágios mais avançados. O diagnóstico é feito através da correlação clinicopatológica: biópsia da lesão cutânea frequentemente revela intenso epidermotropismo, caracterizado por linfócitos CD8+ atípicos, grandes, com halo e núcleo convoluto, contrastando com o infiltrado dérmico leve a moderado. Estas células CD8+, que participam do perfil de resposta T helper-1, impediriam a evolução da doença para o desenvolvimento de placas infiltradas e tumores, além de determinar a inibição da melanogênese nas lesões hipocrômicas. Portanto, a hipocromia poderia ser considerada um marcador de bom prognóstico na micose fungoide.

DOPA-stained melanocytes in the macular lesions of early leprosy

The mechanism of association of hypopigmentation and sensorial loss in a leprosy macular lesions has not been clarified yet. The biopsy of a macular lesion on the medial face of the right forearm of a fourteen-year old male leprosy patient was submitted to DOPA-staining for melanocytes, which is specific for the melanocytic tyrosinase enzyme and it is a proper method for identifying and couting these cells in the skin. A contralateral specimen of the same patient went through the same procedure as a control experiment. The specimen from the macular lesion showed a higher number of DOPA-stained melanocytes than the control fragment. Dermal melanocytes were present in high amounts in the abnormal specimen. Increased expression of tyrosinase by melanocytes in the macular lesions may reflect a positive feed-back stimulus represented by the lack of substance tyrosine, which may in turn be utilized by the myocobacterial agent. Ultrastructural study of the normal and pathological specimens showed no significant differences in the morphological appearance of melanocytes and their melanosomes. These results suggests that the utilization of phenolic compound by the Mycobacterium leprae may be involved in the mechanism of hypopigmentation. A higher number of cases will be necessary to confirm this hypothesis.