Acquired pigmented macules in human piebald lesions. Ultrastructure of melanocytes in hypomelanotic skin.

Two cases of piebaldism are reported. The first patient was a 9-month-old girl with inborn hypopigmented areas on the frontal region of the scalp and both knees. There were no melanocytes in the lesions. In the second case, we observed the patient from 2 months of age for a period of 9 years. Many hyperpigmented spots appeared on the hypomelanotic areas on the frontal region of the scalp, abdomen and both knees. Electron-microscopic examinations of the hypomelanotic skin disclosed an area with regularly distributed melanocytes as well as an area with no melanocytes. Most of the melanosomes were ellipsoidal and lamellar. They were in stage II to III, which signified delayed pigmentation. Hyperpigmented spots were slightly enlarged following PUVA treatment.