This 17-year-old boy presented with eight months of a hyperpigmented, scaly and somewhat reticulate eruption on the chest, back and abdomen.

It was asymptomatic but was unsightly and appeared to be slowly worsening. He was otherwise healthy.

The posterior neck and axillae were clear and the remainder of his skin examination was normal. A scraping for fungus was negative.

What is the most likely diagnosis?