Partial unilateral lentiginosis (PUL) is a rare pigmentary disorder characterized by grouped multiple lentigines on otherwise normal skin that histologically have the typical features of lentigo. This entity has been only rarely reported in the Korean population.

The purpose of this study was to evaluate clinical and histopathologic characteristics, association with other disorders, and differential diagnosis of PUL.

We reviewed our experiences of thirteen cases of PUL which had been collected in our dermatology clinic during the 6-year period between 1993 and 1998.

Twelve patients were female and one was male. In 3 patients the lesions appeared after the age of 20 years. Ten patients had the lesions on the upper part of the body, the neck being the most common location. No bias was shown in terms of the side of the body affected. Cafe-au-lait macules (one to three) were found in six patients, axillary freckles were observed in two. Histopathologic examination of biopsy specimens commonly showed hyperpigmentation of the basal layer, elongation of rete ridges, and an increased number of melanocytes. There ,was no evidence of associated disorders or family history.

Based on this data, we confirmed that PUL is a benign, idiopathic lentiginosis with no commonly associated abnormalities. Furthermore, we believed that PUL is not uncommon in Korean people.