Reticulate hyperpigmentation distributed in a zosteriform fashion: a new clinical type of hyperpigmentation.

We have recently seen two cases of hyperpigmentation in children, which was reticulate and distributed in a zosteriform fashion. As another two cases of hyperpigmentation of this kind in children have been reported previously, described as reticulate hyperpigmentation distributed in a zosteriform fashion, this gives a total of four cases of hyperpigmentation of this kind reported recently from Japan. These four cases differed from progressive cribriform and zosteriform hyperpigmentation, the condition which these cases resembled most closely, with respect to the age of onset of the hyperpigmentation, which in the four Japanese cases was not confined to a dermatome. Like a variant of incontinentia pigmenti (IP), all four cases showed eosinophilia. But they differed from IP in that there was no inflammatory stage, no pigmentary incontinence detectable on histology, and no evidence that the condition was hereditary. These four cases do not conform completely to any described entities and we suggest that they represent a new clinical entity.