Two cases of bizarre acquired localised hyperpigmentation disorders - similar yet different diagnostic challenges: two case reports and a brief literature review.

Cutaneous pigmentation disorders are one of the leading causes of dermatological consultation globally. Hyperpigmentation disorders constitute a group of distinct medical conditions that may be either congenital and associated with various concurrent comorbidities, or acquired due to cutaneous, environmental, or systemic conditions or factors. Due to numerous causes and an often atypical clinical picture, diagnosis can be challenging. Furthermore, although the changes in skin color are not inherently harmful, they can result in significant cosmetic disfigurement and have psychological and social repercussions, particularly given that some hyperpigmentation is irreversible due to the limited effectiveness of current treatments. This article presents two cases exhibiting somewhat similar but different acquired localized hyperpigmentation. We review the current literature with emphasis on the diagnostic approach to this entity and specific acquired hyperpigmentation disorders, in particular drug-induced and paraneoplastic. We emphasize the importance of interdisciplinary cooperation among different specialists, particularly in complicated cases and those that accompany systemic diseases.