Naevus anaemicus (nevus anemicus)

Definition

Naevus anaemicus is a congenital, localised vascular anomaly: a pale area of histologically normal skin whose pallor results from permanent vasoconstriction. Because of the altered vascular response it is also called a "pharmacological naevus".

Occurrence & epidemiology

It is usually noticed in early childhood but is probably present at birth; it occurs in all ethnic groups and is reported more often in females. It is frequent in neurofibromatosis type 1 (prevalence in children with NF1 8.8–51% depending on the study, higher at younger ages) and occurs in phakomatosis pigmentovascularis.

Aetiopathogenesis

The vessels within the lesion are hypersensitive to circulating catecholamines; via α-adrenergic receptors this leads to persistent vasoconstriction. In a transplantation study, the defect lay within the tissue of the naevus itself (donor dominance).

Clinical features

• Usually a single asymptomatic pale patch, round, oval or linear, often with small satellite macules; a mosaic form with multiple lesions appears net-like.
• Mainly on the trunk, in NF1 particularly on the anterior chest wall and often multiple; any body site possible.
• After rubbing, the patch does not redden, while the surrounding skin does.
• Occasionally other vascular anomalies nearby, e.g. a port-wine stain.
• Persists unchanged for life.

Diagnosis

• Clinical diagnosis, supported by the rubbing test.
• Diascopy (pressing the surrounding skin with a glass slide) eliminates the colour contrast.
• A biopsy shows normal skin.
• In children, the finding – especially when multiple – may point to NF1.

Differential diagnoses

• Naevus depigmentosus (achromic naevus)
• Vitiligo
• Piebaldism
• Pityriasis versicolor (tinea versicolor)
• Pityriasis alba
• Idiopathic guttate hypomelanosis

Keep learning in the app

References (selection)

1. DermNet: Naevus anaemicus
2. Nevus anemicus
3. Nevus anemicus: a distinctive cutaneous finding in neurofibromatosis type 1
4. Nevus anemicus. Donor-dominant defect

Cross-references