Asymmetrical periflexural exanthem is a rare clinical condition, seen almost exclusively in children. Very few adult cases have been reported in the literature. We report a case of this rare eruption in an adult man showing characteristic clinical and histological features. Interestingly, this patient also exhibited a pseudoisomorphic Köebner response. Although an infective aetiology of viral origin has been suggested for this localized eruption, the aetiology remains unknown. We are of the opinion that the pseudoisomorphic Köebner response in this patient may support the inoculation hypothesis in the pathogenesis of this disorder.