Author: Wei Wu, Year 5 medical student, The University of Auckland, Auckland, New Zealand. DermNet NZ Editor-in-Chief: Adjunct Assoc. Prof. Amanda Oakley, Dermatologist, Hamilton, New Zealand.
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 and genders. It occurs in approximately 40% of Caucasian infants  and is less often observed in darker-skinned infants . It affects male and female infants equally .
The dermal capillaries in a naevus simplex are dilated due to delay in maturation after neuroectodermal migration and fusion during embryonic development. Reduced regulation by autonomic nerves may be a contributing factor [2,3].
Naevus simplex is present at birth as a single or multiple, flat, pink or red patches, typically with an indistinct, irregular border and blanching on compression [1,2]. They become redder 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 are usually midline  and can be bilateral and symmetrical . They are most commonly found on the nape of the neck, eyelids and glabella . They may also involve the forehead, scalp, nose, lips and back . Naevus simplex is not painful or itchy .
The term ‘naevus simplex complex’ has been proposed for widespread lesions 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 looking for spinal dysraphism 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 this location often also have many similar lesions 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 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, rising to 10% by 1 year of age. It affects female infants more often than males. The haemangioma begins as a pink patch then enlarges. It is most commonly found on the head and neck but may arise on other body sites. Infantile proliferative haemangioma usually resolves after infancy but can leave a residual mark [1,6].
In most sites, naevus simplex fades and disappears within the first 1 to 2 years of life . A lesion on the nape of the neck fades more slowly and incompletely, with a 50% chance of persisting indefinitely [1,5]. As it 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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