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Author: Wei Wu, Medical Student, The University of Auckland, Auckland, New Zealand. DermNet NZ Editor in Chief: Adjunct A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell/Maria McGivern. January 2019.
Naevus simplex is a common, benign capillary vascular malformation. It presents at birth as a pink or red patch and is most often observed on the nape of the neck, eyelid, or glabella [1,2].
Naevus simplex is also called:
Naevus simplex affects infants of all races; it occurs in approximately 40% of Caucasian infants and less often in darker-skinned infants [1,3]. It affects male and female infants equally .
Naevus simplex results from a delay in the maturation of skin cells during embryonic development, following the migration and fusion of cells in the skin nervous system (the neuroectoderm). This results in the characteristic dilation of the dermal capillaries that defines the naevus simplex skin patch. Reduced regulation by autonomic nerves may be a contributing factor in cases of naevus simplex [2,3].
Naevus simplex is present at birth as either single or multiple, flat, pink or red patches, typically occurring with an indistinct, irregular border and blanching on compression [1,2]. Naevus simplex becomes more red with crying, fevers, breath holding, straining, vigorous physical activity, and changes in ambient temperature [1,2,5]. They tend to become less prominent as the child gets older.
The skin lesions usually occur at midline  and can be bilateral and symmetrical in presentation . They are most commonly found on the nape of the neck, eyelids, and glabella, but they may also involve the forehead, scalp, nose, lips, and back [1,2]. Naevus simplex is not painful or itchy .
The term ‘naevus simplex complex’ has been proposed for widespread lesions occurring beyond the common sites .
Midline lumbosacral naevus simplex is sometimes called a ‘butterfly-shaped mark’ and is occasionally observed in a baby with spinal dysraphism. Imaging studies that look for spinal dysraphism (abnormal fusion of the neural tube) may be undertaken if there are other local skin changes such as excess hair growth (localised hypertrichosis), a dermal sinus or pit, a lipoma, or a deviated gluteal cleft, or many similar lesions elsewhere. Infants with a naevus simplex at the lumbosacral midline often also have other similar lesions appearing elsewhere [2,4].
Naevus simplex is occasionally observed in a baby with another condition, such as:
It is uncertain whether there is a true association of naevus simplex with these syndromes [1,4].
Naevus simplex can be diagnosed by its clinical appearance and no further testing is usually required .
Naevus flammeus is a capillary vascular malformation found in 0.3% of newborn infants [1,6]. The lesions present as pink, red or purple patches and can be localised, extensive or multiple [1,6]. Unlike naevus simplex, naevus flammeus tends to be unilateral, often persisting, darkening and thickening with increasing age [1,6].
Infantile proliferative haemangioma is a vascular tumour found in 1.1–2.6% of newborn babies, and it occurs in 10% of infants by 1 year of age. It affects female infants more often than males. The haemangioma begins as a pink patch and then enlarges. It is most commonly found on the head and neck of an infant but may also arise on other body sites. Infantile proliferative haemangioma usually resolves after infancy, but it can leave a residual mark [1,6].
On most body sites, naevus simplex fades and disappears within the first 1–2 years of life . A lesion on the nape of the neck fades more slowly and incompletely, and it has a 50% chance of persisting indefinitely [1,5]. As this site is often covered by hair, it may not be a cosmetic issue.
Pulsed dye laser therapy could be considered to lighten the colour of a persistent lesion .
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