Abstract
A 75-year-old woman on hemodialysis for end-stage renal failure due to polycystic kidney disease developed dark spots on her limbs. She had been treated for extended spectrum beta-lactamase-producing Escherichia coli bacteremia by a rectovaginal fistula and was on long-term oral minocycline (cumulative dose 45 g). Physical examination revealed dark patches on her forearms and lower legs but no trunk hyperpigmentation or visual impairment. Blood tests were normal. Skin biopsy confirmed minocycline-induced hyperpigmentation. Minocycline-induced pigmentation is categorized into types I-IV, each with unique clinical and histopathological features. Types I and II are reversible upon discontinuing minocycline, whereas types III and IV are permanent. The patient was diagnosed with type II pigmentation, generally occurring with a cumulative dose exceeding 70-100 g; however, her lower dose (45 g) led to pigmentation, possibly influenced by her vitamin D deficiency. Clinicians should evaluate the antimicrobial indication and treatment period, considering not only the benefits but also the side effects and antimicrobial resistance. If minocycline is used, attention should be paid to minocycline-induced hyperpigmentation, and this possibility should be communicated to patients to enable early detection.