Ephelide Freckle

Freckles, or ephelides, are small, red-brown macules scattered over skin exposed to the sun. Exposure to the sun deepens the pigmentation of freckles, in contrast to lentigo simplex, whose already deep pigment does not change. Ephelides, simple lentigines, and solar lentigines are difficult to distinguish from one another clinically and are considered together in most clinical and epidemiologic studies. Taken together, these lesions constitute a significant risk factor for the development of melanoma .

Histopathology.

 Freckles show hyperpigmentation of the basal cell layer, but in contrast to lentigo simplex, there is no elongation of the rete ridges and, by definition, no obvious increase in the concentration of melanocytes. However, in a quantitative study of lesions from children, melanocyte frequencies in freckles were significantly greater than in adjacent nonpigmented skin. Cellular atypia of melanocytes and reactivity of melanocytes for HMB­45 were noticed in some freckles . It is likely that freckles represent a hyperplastic and hyperactive response of melanocytes to ultraviolet (UV light).

Histogenesis

On electron microscopy, the melanocytes within freckles are found to be essentially similar to those of dark-skinned persons. Melanocytes of the surrounding epidermis, by contrast, show constitutionally few and minimally melanized melanosomes, many of which are rounded rather than elongated . Such rounded melanosomes (so-called pheomelanosomes) are characteristic of the lightly pigmented skin of individuals with red hair and/or blue eyes and a cutaneous phenotype that is prone to freckles. As noted earlier, the tendency to develop freckles appears to be closely related to MC1 R gene polymorph isms .