Partial Unilateral Lentiginosis: A Systematic Review of 159 Reported Cases and Diagnostic Considerations.

Partial unilateral lentiginosis is a rare pigmentary disorder characterized by multiple lentigines confined to one side of the body and is frequently misdiagnosed as nevus spilus or segmental neurofibromatosis type 1. Despite its benign nature, its distinctive distribution, often involving visible areas such as the face and neck, may result in cosmetic concern and diagnostic uncertainty. A systematic review was conducted to synthesize all published cases of partial unilateral lentiginosis. PubMed and Embase were searched from 1983 to 2026 for case reports and case series describing clinically or histopathologically compatible cases. Data on patient demographics, clinical features, associated findings, histopathology, and treatment outcomes were extracted. A total of 159 patients were identified. The condition most commonly presents in childhood, with unilateral lentigines arranged in dermatomal or Blaschko linear patterns. Histopathologic findings were most frequently consistent with lentigo simplex. Reported associations included café-au-lait macules, Lisch nodules, ocular pigmentation, seizures, and rare systemic conditions. The main diagnostic challenge was distinguishing partial unilateral lentiginosis from nevus spilus and mosaic or segmental neurofibromatosis type 1. Management approaches were variable, with laser-based therapies demonstrating partial to near-complete clearance in small series. Recurrence and post-inflammatory hyperpigmentation, particularly in darker skin phototypes, were notable limitations. This review provides a comprehensive overview of the clinical presentation, associated findings, diagnostic considerations, and treatment outcomes of partial unilateral lentiginosis.