Eruptive Lentiginosis Within Resolved Psoriasis Plaques: A Case Report and Systematic Review of the Literature

BACKGROUND: Many patients with psoriasis suffer from post-inflammatory pigmentary alteration (PIPA), which remains an unmet treatment need. Eruptive lentiginosis (EL) is a rare form of PIPA where multiple dark brown macules arise within a resolving psoriatic plaque. We present a case of a 68-year-old male with a history of chronic plaque psoriasis and prothrombin deficiency, who developed extensive EL following ixekizumab treatment. In addition, this article will discuss the current literature on risk factors, clinical outcomes, and treatments for EL. METHODS: The systematic literature review, conducted in accordance with PRISMA guidelines, utilized three databases, PubMed, SCOPUS, and CINAHL Plus, using search terms "psoriasis" and "lentigines" or "lentiginosis". A total of 26 articles were identified and included. RESULTS: EL was reported in a diverse patient population with various Fitzpatrick skin types and ages ranging from 5 to 74 years old. Additionally, EL has developed in a wide array of treatments, including PUVA, NB-UVB, cyclosporine, acitretin, methotrexate, topicals, and biologics, with TNF inhibitors being the most common. DISCUSSION: The mechanism of EL is likely multifaceted, with potential mediators, such as UV radiation and inflammatory cytokines (TNF-α, IL-17, and IL-23), which may stimulate melanocyte proliferation. Additionally, our patient’s history of prothrombin deficiency suggests possible interplay between the coagulation cascade and melanogenesis in EL development. Patients and providers alike should be aware of the clinical course of EL, which, unlike other forms of PIPA, tends to persist without treatment. Potential treatment options for EL include the Q-switched ruby laser, which can lead to partial improvement. .