Linear and Whorled Nevoid Hypermelanosis with Depigmentation.

Linear and whorled nevoid hypermelanosis (LWNH) is a rare disorder of pigmentation characterized by hyperpigmented macules in a linear or whorled streaky configuration. Lesions are distributed mainly on the trunk and extremities, sparing the palms, soles, and mucosae. Depigmentation occurring in the pre-existing whorls has not been reported till date. Herein, we report one such rare case of familial LWNH with depigmentation.

Introduction

Linear and whorled nevoid hypermelanosis (LWNH) is a rare sporadic pigmentary anomaly, characterized by swirls and streaks of macular hyperpigmentation following the lines of Blaschko, without preceding inflammation, and is usually seen in the first 2 years of life.[1] The condition was first described in 1988 by Kalter et al.[1] Synonyms include zosteriform hyperpigmentation, zosteriform lentiginous nevus, zebra-like hyperpigmentation, reticulate hyperpigmentation of Iijima, and nevoid hyperpigmentation following Blaschko lines.[12]

Case Report

A 22-year-old male presented to the outpatient department with chief complaints of asymptomatic, dark-colored skin lesions over the body since 10 years of age. According to the patient, the lesions first appeared over both his arms and progressed within the next 2 years to involve the trunk and lower limbs. The lesions darkened with age and no new lesions appeared over the next 9 years; however, over the last 1 year he started noticing multiple white-colored, pinpoint lesions appearing over the hyperpigmented lesions without any preceding skin itching or redness. There was no history of warty lesions or blisters prior to the appearance of these lesions. There was no history suggestive of any recurrent lower respiratory infections or involvement of the cardiovascular and the central nervous systems. The patient described presence of similar dark-colored skin lesions involving the trunk, arms, and legs in his mother without a history of any light-colored patches. There was no history of consanguinity or recurrent fetal deaths in the family. There was no history of vitiligo or other autoimmune disorders in the family.

Systemic examination was unremarkable. Cutaneous examination revealed presence of multiple, whorled, hyperpigmented macules, arranged bilaterally and symmetrically, along the lines of Blaschko on the abdomen, chest, and back [Figure 1]. Similar lesions were arranged linearly on the extensor and flexor aspects of the arms and legs. Multiple pinpoint depigmented macules were seen along the areas of streaky macular pigmentation [Figure 1]. The texture of skin was normal over the streaks, the intervening skin, and over the depigmented areas. No clinical signs of Koebner phenomenon or any leukotrichia were visible.

Figure 1

Classical whorled, hyperpigmented macules along the lines of Blaschko on the trunk with pinpoint areas of depigmentation

Hematological and routine biochemical tests revealed no abnormalities. Histopathological evaluation of the depigmented lesion showed complete absence of melanocytes [Figure 2a]. However, the pigmented macules revealed increased pigmentation of the basal cell layer with melanocytes present up to the mid-epidermis [Figure 2b]. No focal areas of pigmentary incontinence were noticed in the dermis. Based on clinicopathological correlation, a diagnosis of LWNH with punctate hypopigmentation was made. The individual was reassured of the benign nature of the disorder. However, treatment for depigmented areas with narrow band ultraviolet B radiation and topical corticosteroids was advised. A periodic follow-up was recommended at our dermatology unit. However, the patient was lost to follow up.

Figure 2

Picture collage showing histopathological examination (a) complete absence of melanocytes in the depigmented area (b) abundance of melanocytes in the hyperpigmented area (H and E, ×40)

Discussion

Linear and whorled nevoid hypermelanosis is a rare disorder of pigmentation characterized by hyperpigmented macules in a linear or whorled streaky configuration.[3] Onset is within a few weeks of age, with no preceding inflammation or palpable lesion. The usual age of the onset of hyperpigmentation is within the first few weeks of life, which continues to progress for a year or two before stabilization.[14] Clinically, reticulate hyperpigmented macules coalescing to form streaks and whorled areas are seen over the trunk, extremities, and neck following the lines of Blaschko. The macules may become less prominent with age in some patients. Streaks and whorls follow the lines of Blaschko and do not cross the midline. The pigmented streaks display a V-shaped pattern over the spine, an S-shaped or whorled pattern over the anterior and lateral aspects of the trunk, and a linear arrangement over the extremities and genitalia.[5] There is sparing of the face, palms and soles, eyes, and mucous membranes.

Extracutaneous features include skeletal, neurological, and ocular abnormalities. Central nervous system diseases include microcephaly, arhinencephaly and epilepsy whereas cardiac defects include ventricular septal defect and tetralogy of Fallot. Developmental retardation, facial and body asymmetry, deafness, and brachydactyly have been mentioned in the literature in association with LWNH.[67]

Histopathology reveals diffuse moderate hyperpigmentation in the basal layer and prominence or vacuolization of melanocytes. Pigmentary incontinence is usually, but not always absent. Genetic studies suggest somatic mosaicism as a cause for LWNH with mosaic trisomy of 7, 14, 18, 20; X-chromosomal mosaicism has been reported.[8]

The differential diagnosis includes incontinentia pigmenti, hypomelanosis of Ito, and epidermal nevus. Dermatoscopic feature mentioned include “net like” pattern of pigmentation in both linear and whorled parts by Naveen et al., and Ertam et al. described a “parallel” pattern which consisted of linear or circular arrangement of parallel whorled streaks along lines of Blaschko.[910]

Explanation for appearance of the depigmented macules is not clear. Monogenic skin disorders are the ones commonly described with lines of Blaschko, however, polygenetic skin disorders such as psoriasis, lichen planus, segmental vitiligo, granuloma annulare, etc. can also present in similar patterns.[11] Literature search reveals an entity called as Blaschkolinear vitiligo, which has been described in association with segmental vitiligo, acrofacial vitiligo, and non-segmental vitiligo. Kovacevic et al. have reported a new entity called as “mixed vitiligo of Blaschko lines,” where they discussed presence of segmental and non-segmental vitiligo in Blaschkolinear pattern.[12]

Till date, no cases of LWNH with areas of depigmentation have been mentioned in the literature, and to the best of our knowledge, this is most probably the first case report of familial LWNH superimposed by pinpoint spots of depigmentation.

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Conflicts of interest

There are no conflicts of interest.