Transepidermal elimination in exogenous ochronosis. A report of two cases

Exogenous ochronosis is caused by the long-term application of skin-lightening creams containing hydroquinone. This irreversible disfiguring cosmetic problem assumes epidemic proportions in South African blacks. Mild ochronosis is characterized clinically by coarsening and darkening of the skin; severe ochronosis, by coalescing, caviar-like black papules and atrophy. Histology shows ochronotic collagen fibers with eventual formation of ochronotic colloid milium. A variable cellular infiltrate, which may be granulomatous, is present. We describe two patients with severe exogenous ochronosis who developed superimposed papular lesions. Histology in both cases showed transfollicular elimination of ochronotic fibers. In one patient, gross epidermal hyperplasia, a dense lichenoid infiltrate, and partial destruction of ochronotic fibers accompanied the process of elimination (cell-rich type). In the other, concomitant epidermal hyperplasia and a cellular infiltrate were absent (cell-poor type). Further studies are needed to prove or disprove the existence of such a proposed subdivision. Transepidermal elimination in exogenous ochronosis has been mentioned in a previous report, but to our knowledge this is the first detailed documentation of this phenomenon. The clinical and histopathological spectrum of exogenous ochronosis is thus expanded.