Itchy patch below the umb...

A 59-year-old bus driver presents with a 5-month history of a persistent itchy patch below his umbilicus. Initially it began as an intermittent eruption, coming and going in an apparently random pattern; over the past six weeks, since the weather became warmer, it has persisted. He is otherwise well with no history of previous skin problems. He is not on medication.

Examination 

There is a localized area of marked lichenification, post-inflammatory hyperpigmentation, excoriation and erosion at the midline below his umbilicus. The surrounding skin has a more diffuse area of low-grade lichenification, hyperpigmentation and mild erythema.