Nevoid Hypermelanosis, Linear And Whorled

Description

Linear and whorled hypermelanosis (LWNH) is a benign skin condition characterized by onset in infancy of hyperpigmented regions composed of small light brown spots that coalesce with age and follow the lines of Blaschko on the trunk and limbs. The soles, palms, face, and mucous membranes are spared. The lesions are asymptomatic and progress with age; affected individuals have no accompanying extradermal features. There is no previous history of inflammation on affected areas (summary by Kalter et al., 1988).

Clinical Features

Iijima et al. (1987) reported 2 unrelated Japanese children with early-onset reticulate hyperpigmentation distributed in a zosteriform pattern along the lines of Blaschko on the trunk and limbs, but sparing the face, palms, and soles. The first girl presented at age 4 months with a history of the pigmentation beginning at age 1.5 months. She had no other abnormalities except for mild crowding of some baby teeth. The areas of hyperpigmentation were formed by a coalescence of light brown 1- to 2-mm irregular spots with clearly defined borders and no variation in color. Skin biopsy showed increased melanin in the basal layer, but no increase in melanocytes and no melanophages. Her mother and brother had nevus spilus. The second child was a 5-year-old girl with small asymptomatic pigmented spots that appeared on the insides of both lower legs at age 2, which then gradually expanded to involve the thighs, upper limbs, and trunk in a zosteriform pattern. The affected regions consisted of irregular brown 2- to 3-mm spots with clearly defined borders and partially fused to produce a reticulate pattern. Light microscopy showed an increase in melanin in the basal layer, but no melanophages. Both patients had mildly increased peripheral eosinophils. Neither child had any other abnormalities or family history of a similar disorder, and the features could be distinguished from other known pigmentary disorders, particularly incontinentia pigmenti (IP; 308300). Iijima et al. (1987) noted that the entity was most similar to progressive cribriform and zosteriform hyperpigmentation (PCZH; see below) described by Rower et al. (1978), except that it was more extensive and showed earlier onset compared to the latter cases.

Kalter et al. (1988) reported 2 unrelated individuals with what they termed congenital linear and whorled nevoid hypermelanosis (LWNH). A 12-month-old Caucasian girl developed brown streaks on her ankles soon after birth, which gradually spread to involve most of her body asymmetrically, but along the lines of Blaschko. Follow-up until age 6 years showed that the lesions grew in size with her and darkened with sun exposure. All other aspects of development were normal. The hyperpigmentation consisted of 1- to 5-mm light brown macules and streaks especially obvious on the flanks and sparing the palms, soles, and mucous membranes. Skin biopsy showed increased basal layer pigmentation with normal basal melanocytes that were somewhat increased in number. Electron microscopy showed an increase in the number of melanosomes in the hyperpigmented skin. There was no family history of a similar disorder. A 6-month-old Indian boy had a similar condition beginning at 2 to 3 weeks of age. The first patient had mildly increased peripheral eosinophil counts on 1 occasion. Chromosome analysis of cultured lymphocytes from both patients showed no evidence of mixoploidy or chimerism, and cytogenetic analysis of cultured fibroblasts showed no detectable chromosomal changes. Kalter et al. (1988) distinguished the disorder from hypomelanosis of Ito (HMI; 300337), but suggested that LWNH may reflect mosaicism of neuroectodermal cells.

Bjorngren and Holst (1991) reported a 15-year-old Caucasian girl with reticulate hyperpigmentation similar to that reported by Iijima et al. (1987). She presented for acne evaluation and was found to have hyperpigmentation of several body regions, including the trunk, arms, and legs. The changes were light brown 2- to 3-cm spots, irregular in shape with clearly defined borders. They had coalesced to form streaks and whorls symmetrically. Microscopic analysis showed increased granular pigment in the cytoplasm at the base of the rete ridges, but no increase of melanocytes. History revealed a 7 x 10-mm nevus spilus in infancy and a 2- to 3-mm woolly hair nevus on the scalp at age 3. Di Lernia et al. (1992) suggested that the patient reported by Bjorngren and Holst (1991) more likely had progressive cribriform and zosteriform hyperpigmentation, as described by Rower et al. (1978), due to the later onset. Di Lernia et al. (1992) emphasized that PCZH and LWNH are likely part of the same disorder.

Di Lernia (2007) reported a retrospective review of 16 unrelated children referred for segmental, linear, or swirled hyperpigmentation distributed along the lines of Blaschko. Six patients had classic LWNH with onset in infancy of progressive widespread hyperpigmentation. Ten patients had later onset of unilateral hyperpigmentation, which Di Lernia (2007) considered to be consistent with PCZH. The hyperpigmentation was not preceded by inflammation in any case. Histologic studies showed a mild increase of melanin in the basal layer of the epidermis and mild elongation of the rete ridges. Other abnormalities were found in 2 patients: 1 had severe developmental delay with autism, and the other had onset in adolescence of atrophic gastritis and anorexia nervosa. Additional anomalies were not found in any other patient. Di Lernia (2007) noted the overlap of LWNH and PCZH with hypomelanosis of Ito, which is characterized by hypopigmentation in a linear and whorled pattern following the lines of Blaschko and believed to result from somatic mosaicism, and suggested that all 3 conditions represent 1 entity, that of 'pigmentary mosaicism.'

Progressive Cribriform and Zosteriform Hyperpigmentation

Rower et al. (1978) reported 5 unrelated patients with progressive cribriform and zosteriform hyperpigmentation (PCZH). Age at onset ranged between 10 and 18 years. The lesions were composed of light brown spots with increased basal layer pigmentation on microscopy. The lesions were located on the lower thighs or torso, were confined to 1 side of the body, and showed gradual extension with time. None of the patients had other abnormalities and the condition was benign.

Inheritance

Most cases of LWNH occur sporadically. However, Akiyama et al. (1994) reported a Japanese mother and daughter with the condition. Asymptomatic hyperpigmented macules in a streaky configuration appeared on the trunk and extremities in both patients several weeks after birth and then gradually spread. Light microscopy showed a slight increase in the number of melanocytes in the epidermis and irregular basal melanosis. Ultrastructural studies showed an increase in the number of normal-appearing melanosomes in keratinocytes. Chromosome analysis of peripheral blood cells and dermal fibroblasts showed no evidence of chimerism.

Metta et al. (2011) reported an Indian family in which a 12-year-old girl, her 45-year-old mother, and the 65-year-old maternal grandmother all had asymptomatic LWNH with onset in infancy and gradual progression. The mother and grandmother had a history of the lesions fading over time. None of the patients had accompanying features. Genetic studies showed trisomy 20 in the mother's blood, but this was not found in the child.