Histopathological differences between early and old lesions of hyperkeratosis Lenticularis Perstans (Flegel's disease).

A case of hyperkeratosis lenticularis perstans (Flegel's disease) was studied histopathologically comparing early and old lesions. The age of the lesions were judged by both the patient's history and direct observation. The histopathologic and immunophenotypic features of a new lesion were essentially in accordance with previous findings. However, the old lesion had obviously different pathologic features. These included the absence of epidermal atrophy and infiltrate in the upper dermis under the lesion. Ultrastructural studies revealed that the presence of many normal-appearing membrane-coating granules in the keratinocytes of the old lesion, whereas the organelles were not found in the keratinocytes of the early lesion.