Small lesions of porokeratosis show a normal proliferation rate with MIB-1.

AIM: Cornoid lamella is the hallmark of the group of conditions encompassed by the term porokeratosis (PK). One of the characteristics of cornoid lamella is parakeratosis. Although these explanations are not universally accepted, dermatopathology suggests that parakeratosis is formed either by the acceleration of epidermopoiesis or the faulty maturation of keratinocytes. This study tested the proliferation rate of the cell population underneath the cornoid lamella.

METHOD: An immunohistochemical study was performed in four cases of PK (2 plaque type PK, 1 disseminated superficial actinic PK, and 1 linear PK) with the MIB-1 antibody. The lesions evidenced in the patients were all smaller than 2 cm.

RESULTS: The epidermal cells beneath the cornoid lamella showed a proliferation rate that was similar to the one observed in the adjacent epidermal cells in all cases.

CONCLUSIONS: These findings support the premise that hyperproliferation of keratinocytes is not needed for the genesis of the cornoid lamella.