We report the case of a healthy 16-year-old male with progressively increasing brown macules arranged in a zosteriform pattern on the left abdomen and back. The lesion appeared at the age of 15 and has been enlarged since then. He had no history of any preceding eruption or injury to the area. He had no evidence of internal diseases. His family had no history of skin abnormalities. He was not taking any medications. Physical examination revealed linear, cribriform, brown macular pigmentation arranged in a zosteriform pattern on the left abdomen and back ( fig. 1). All macules were uniformly tan. Laboratory studies, including complete blood cell count, liver and renal function tests and serum electrolyte, had negative results. A skin boipsy specimen from the abdomen revealed increased pigmentation within the basal keratinocytes. There were a few dermal melanophages. No nevus cells were present ( fig. 2). Fontana-Masson stain showed an increase in melanin in the basal keratinocytes. The diagnosis of progressive cribriform and zosteriform hyperpigmentation -the late onset linear and whorled nevoid hypermelanosis was made. No treatments were given.Progressive cribriform and zosteriform hyperpigmentation was first described by Rower and colleagues in 1978. 1 The following criteria were suggested: (1) uniformly tan cribriform macular pigmentation in a zosteriform distribution; (2) a histologic pattern that consisted of a mild increase in melanin pigment in the basal cell layer and complete absence of nevus cells; (3) no history of rash, injury, or inflammation to suggest postinflammatory hyperpigmentation; (4) onset well after birth with gradual extension -age at onset was in the second decade of life in every case; and (5) lack of other associated cutaneous or internal abnormalities. 1 Linear and whorled nevoid hypermelanosis was first described by Kalter and colleagues in 1988. 2 It is characterized by swirls and streaks of macular hyperpigmentation along the lines of Blaschko. It usually appears early during the first year of life. In some patients, the lesions are quite stable, while in others they spread but then stabilize by the age of 2-3. The linear hyperpigmentation tends to persist indefinitely. Occasionally, there are associated systemic abnormalities. 2 Somatic mosaicism that develops during embryogenesis appears to be the underlying aetiology. The linear nature of the pigmented bands probably reflects the clonal migration and proliferation of embryonic melanocyte precursors (melanoblasts). 3 Recently, linear and whorled nevoid hypermelanosis have been used to encompass a wide spectrum of clinical entities, ranging from the congenital or perinatal form of Kalter and colleagues to the segmentary and delayed form of Rower and colleagues, for which there is a tendency to use the term progressive cribriform and zosteriform hyperpigmentation. 4 We report herein a case of progressive cribriform and zosteriform hyperpigmentation -the late onset linear and whorled nevoid hypermelanosis which is not associated with ...