Epidermal naevus and naevus sebaceous — SAQ

Stem

A 6-year-old girl is brought to clinic with a long-standing, intensely itchy, red, scaly, linear plaque running down the medial aspect of her left lower leg. The lesion has been present since infancy and has gradually lengthened as she has grown. It is more symptomatic in winter. Her mother has tried topical hydrocortisone 1% cream with little benefit. On examination there is a well-demarcated, erythematous, scaly, linear plaque approximately 8 cm long following an S-shaped course on the lower limb. The rest of the skin examination is normal, and the child is otherwise well with normal growth and development.

Questions

a) What is the most likely diagnosis, and what clinical features support it? (2 marks)

b) What is the pathophysiological basis for the distribution of this lesion? (2 marks)

c) How would you distinguish this condition from linear psoriasis? (3 marks)

d) Outline the management options for this patient. (3 marks)

Model answer (must-hit points)

^[1]a) Diagnosis and supporting features (2 marks)

• Inflammatory linear verrucous epidermal naevus (ILVEN) — 1 mark.
• Supporting features: congenital or early-infancy onset; intensely pruritic; erythematous, scaly, psoriasiform linear plaque; follows Blaschko's lines; refractory to low-potency topical corticosteroid — 1 mark.

^[1][3]b) Pathophysiological basis for distribution (2 marks)

• Epidermal naevi arise from postzygotic somatic activating mutations in keratinocyte growth-regulating genes — 1 mark.
• The mutated clone expands and migrates along Blaschko's lines (embryonic ectodermal cell migration tracks), producing a linear or S-shaped distribution — 1 mark.

^[2]c) Distinguishing ILVEN from linear psoriasis (3 marks)

• History: ILVEN is present from infancy; linear psoriasis usually develops in a patient with or at risk of psoriasis and may follow trauma (Koebner phenomenon) — 1 mark.
• Symptoms: ILVEN is typically more intensely pruritic and refractory to topical corticosteroids; psoriasis usually responds to topical steroids and calcipotriol — 1 mark.
• Associated features: psoriasis may have nail changes, scalp involvement, or arthropathy; ILVEN is an isolated linear lesion. Histology of ILVEN can be indistinguishable from psoriasis, so the diagnosis is clinical — 1 mark.

^[1]d) Management options (3 marks)

• First-line: trial of topical calcipotriol 0.005% ointment once or twice daily and/or a potent topical corticosteroid such as betamethasone dipropionate 0.05% ointment for short courses — 1 mark.
• Second-line: topical retinoids (e.g., tretinoin 0.05% cream) or, for small lesions, full-thickness surgical excision with primary closure — 1 mark.
• Refractory or extensive disease: laser ablation (CO2 or erbium:YAG) or dermabrasion for cosmetic improvement, with counselling that recurrence is common; regular follow-up and reassurance if asymptomatic — 1 mark.

References3ShowHide

1. [1]Atzmony L, Ugwu N, Hamilton C, et al. Inflammatory linear verrucous epidermal nevus (ILVEN) encompasses a spectrum of inflammatory mosaic disorders Pediatr Dermatol, 2022.PMID 35853659
2. [2]Zakrzewski JL, Luecke T, Bentele KH, et al. Epidermal naevus and segmental hypermelanosis associated with an intraspinal mass: overlap between different mosaic neuroectodermal syndromes Eur J Pediatr, 2001.PMID 11686504
3. [3]Atzmony L, Ugwu N, Hamilton C, et al. Inflammatory linear verrucous epidermal nevus (ILVEN) encompasses a spectrum of inflammatory mosaic disorders Pediatr Dermatol, 2022.PMID 35853659