Expression of the c-kit receptor in hypomelanosis: a comparative study between piebaldism, naevus depigmentosus and vitiligo.

In order to investigate possible alterations in c-kit protein expression on epidermal melanocytes in different hypopigmentary disorders, we have examined skin specimens from one patient with piebaldism, one patient with naevus depigmentosus, and five patients with vitiligo. Cryosections were examined by immunohistochemistry using monoclonal antibodies against the c-kit protein (YB5.B8) and melanosomes (TA99). In piebaldism, hypomelanotic epidermis contained only a few TA99-positive epidermal melanocytes and no detectable c-kit protein, whereas in naevus depigmentosus the expression of c-kit protein was strong, and TA99 immunoreactivity was faint. In vitiligo lesions, no epidermal immunoreactivity for melanosomes or c-kit protein was found. Normally pigmented skin of all patients showed immunoreactivity of epidermal melanocytes for both c-kit protein and melanosomes. Different hypomelanotic lesions can thus be differentiated by absent melanocyte c-kit protein and low or no expression of melanosomal marker in piebaldism, normal c-kit but low melanosome expression in naevus depigmentosus, and the absence of all melanocyte markers in vitiligo.