Segmental Speckled Lentiginous Nevus Exacerbated by Pregnancy in an Otherwise Healthy Female: A Case Report

Speckled lentiginous nevi (SLN), or nevus spili, are seen in 0.2% to 2.3% of the population, presenting as tan patches with overlying hyperpigmented macules or papules in a speckled arrangement. Segmental SLN represent a small subset of SLN, with the segmental type comprised of larger, unilateral lesions that may rarely give rise to melanomas and have been reported to proliferate in response to ultraviolet light exposure. We present the case of a 40-year-old woman who presented with dark brown macules and papules scattered in a sharp, unilateral distribution on her back, chest, and abdomen. The lesions had been present for 10 years but had enlarged and darkened during her previous pregnancies. A clinical diagnosis of segmental speckled lentiginous nevus was made, and the patient was given appropriate instructions for sun protection and proper follow-up. This is the second reported case of segmental SLN with morphologic changes during pregnancy, suggesting an underlying hormonal component in its pathogenesis. Introduction Speckled lentiginous nevus (SLN), also referred to as nevus spilus, is a relatively common skin lesion, occurring in 2.3% of adults.1 SLN lesions present as numerous, hyperpigmented macules and papules over tan-brown patches.2 SLN has recently been categorized into macular and papular subtypes, known as nevus spilus maculosus and nevus spilus papulosus, respectively.3 Segmental SLN are large lesions that present in a unilateral or zosteriform distribution. Such cases typically present at birth or in infancy and may worsen secondary to ultraviolet (UV) light exposure.4 These have been reported to give rise to single or multiple melanomas, although this is rare.4,5 In this case report, we present a 40-year-old female with adult-onset segmental SLN that worsened during pregnancy, review the disease’s pathogenesis and management, and provide diagnostic pearls. Case Report A 40-year-old, otherwise healthy woman presented with a 10-year history of dark brown macules and papules on the right side of her torso. The lesions were asymptomatic but were noted to become darker and larger during past pregnancies. No previous workup or treatments had been attempted. A full review of systems, including visual changes, hearing loss, neurologic abnormalities, and musculoskeletal changes, was negative. Physical examination revealed a female with Fitzpatrick type IV skin with a unilateral distribution of brown macules and papules in a speckled arrangement with background hyperpigmentation over the right side of the back, chest, and abdomen (Figures 1, 2). No epidermal nevi or port wine stains were noted. Due to the asymptomatic nature of the lesions and their clinical presentation, a clinical diagnosis of segmental speckled lentiginous nevus was made. The patient was educated on the importance of sun protection and close monitoring of her skin lesions with annual skin examinations. Discussion Despite continuing debate over the nosology of speckled lentiginous nevi (SLN) among melanocytic lesions, the etiology is likely multifactorial, with genetic and environmental factors playing a role.6 Approximately 80% are present at birth or shortly after,7 leading some authors to categorize SLN as a congenital melanocytic nevus, while others believe it to be an acquired process because the characteristic speckled hyperpigmentation may take years to develop.6 Segmental or “zosteriform” presentations of SLN are also believed to be caused by somatic mosaicism, which consists of genetically distinct populations of cells that result from post-zygotic somatic mutations. Recently, activating mutations of HRAS were identified in smaller SLN lesions, whereas an activating missense NRAS mutation was identified in a case of congenital segmental SLN.8,9 Environmental factors also influence established SLN lesions. Ultraviolet (UV) light exposure has been reported to darken the lentiginous background hyperpigmentation and cause proliferation of the speckled macules and papules.4 Additionally, in one case series, melanomas arising within segmental SLN occurred only in sun-exposed areas, which may be explained by epigenetic modification of tumor suppressor genes in lesional skin.4 Our patient reported darkening and enlargement of her SLN during pregnancy, which to our knowledge has been reported in only one other case.10 Of note, the other case of SLN worsened by pregnancy had a congenital onset, whereas our patient reported adult-onset of her SLN. There are similarities between the SLN in our patient and general characteristics of melasma, a hyperpigmentation disorder that commonly affects women’s faces secondary to hormonal changes, including those associated with pregnancy or oral-contraceptive use. Melasma occurs more frequently in darker pigmented individuals (Fitzpatrick III-V), may be triggered by sun exposure and pregnancy – suggesting hormones may have played a role in the hyperpigmentation component our patient’s SLN -and has a genetic component, with 40% of affected patients reporting relatives also affected by the disease.11 A meticulous physical examination can give the clinician several important clues for the diagnosis of SLN and associated disorders. The underlying patch, a key finding in SLN, is absent in clinically similar disorders like agminated nevus and partial unilateral lentiginosis (also known as segmental lentiginosis).5 Macular versus papular Figure 1. Dark brown macules and papules in a speckled, unilateral distribution overlying background hyperpigmentation with two associated café-au-late macules. Figure 2. Dark brown macules and papules in a speckled distribution overlying background hyperpigmentation on the right side of the