Naevus sebaceous

ICD-11

LC02

Synonyms

Naevus sebaceous of Jadassohn.

Epidemiology

Affects 0.3% of newborns. The prevalence is equal in males and females. Most frequent scalp lesion in newborns and childhood.

Definition

A congenital epidermal hamartoma that comprises sebaceous, follicular, and apocrine elements.

Aetiology & Pathogenesis

Postzygotic somatic mutations of the Ras gene family, most commonly HRAS,less common KRAS.

Signs & Symptoms

At birth: a slightly raised, solitary plaque with a smooth, yellowish surface. Most commonly present on the scalp ,hairloss at the site. At puberty, the lesion becomes thicker, and the surface is more verrucous. In adulthood, neoplasms (most commonly benign) may develop within the lesion.

Localisation

Most commonly scalp area (90%), but it may also appear on the face and neck and rarely on the trunk.

Classification

None. Association with syndromal constellation: Schimmelpenning-Feuerstein-Mims syndrome, Didymosis aplasticosebacea.

Laboratory & other workups

Not necessary. Genetic counselling may be necessary in some cases.

Dermatopathology

In infancy: epidermal changes include acanthosis and papillomatosis; pilosebaceous units are immature. At puberty: the epidermis becomes more hyperplastic, papillomatous, and verrucous. Numerous sebaceous glands with an increased number of sebaceous lobules are found in the superficial dermis.

Course

See symptoms.

Complications

In adulthood, secondary neoplasms may develop. The most common tumour within the naevus sebaceous is trichoblastoma, followed by syringocystadenoma papilliferum. Basal cell carcinoma develops in less than 1% of lesions.

Diagnosis

History; clinical features.

Differential diagnosis

In early infancy: aplasia cutis congenita, mastocytoma. In later stages: epidermal nevus, congenital nevus, sebaceoma, seborrheic keratosis, verruca vulgaris, juvenile xanthogranuloma.

Prevention & Therapy

Observation, surgical excision (depending on the size and location of the tumour).

Special

None.

3.1.5 Naevus sebaceous