DISEASE CARD

Definition

Annular epidermolytic ichthyosis (AEI) is a rare clinical variant of epidermolytic ichthyosis (EI) (see ichthyosis classification) characterized by the presence of a blistering phenotype at birth and the development of annular polycyclic erythematous scales on the trunk and extremities in early infancy.¹

Clinical description

At birth, clinical features are similar to those of classical EI with erythroderma, blistering and superficial skin erosions at sites of minor trauma. Diffuse hyperkeratosis on flexural sites and extensor surfaces can occur as well as palmoplantar hyperkeratosis. From early infancy on, patients show outbursts of annular polycyclic erythematous plaques with scales (psoriasiform) on the trunk and extremities but may coalesce to involve most of the body surface. They can persist for several weeks or even months. In contrast to EI, periods of almost complete clearing between the outbursts are typical (except for palmoplantar keratoderma in patients with KRT1 mutations). Phenotypic heterogeneity has been described. Generally, AEI is considered milder in comparison to EI, although hyperkeratosis on palms and soles progressively thickens in patients with KRT1 mutations. ^{2, 3}

Pathogenesis

The disease is caused by mutations in the KRT1 (12q13.13) and KRT10 (17q21.2) genes, encoding keratins 1 and 10 respectively. These mutations impair keratin filament formation and weaken the structural stability of the keratinocyte cytoskeleton.^{4, 5}

Diagnosis

Mutation analysis in suspected cases is often necessary for confirmation of the diagnosis. Histologic features are similar to other keratinization disorders and include orthokeratotic hyperkeratosis, prominent acantholysis and thickened granular layer with coarse keratohyalin granules.

Treatment

Therapy is limited to symptomatic treatment options that include daily use of emollients, retinoids (oral, topical), topical glucocorticoids, calcipotriene, and keratolytics. Treatment response may vary among patients and families.^{2, 3, 6}

References

^{1.    Sahn EE, Weimer CE, Jr., Garen PD. Annular epidermolytic ichthyosis: a unique phenotype. J Am Acad Dermatol. 1992;27(2 Pt 2):348-355.
2.    Liang B, Yuan T, Zhou Y, et al. Annular epidermolytic ichthyosis with palmoplantar keratosis: a unique phenotype associated with interfamilial phenotypic heterogeneity. Eur J Dermatol. 2020;30(3):294-299.
3.    Reolid A, Carrasco L, Noguera-Morel L, et al. Annular epidermolytic ichthyosis: An exceptional mild subtype of epidermolytic ichthyosis without genotype and phenotype correlation. JAAD Case Rep. 2020;6(1):46-50.
4.    Joh GY, Traupe H, Metze D, et al. A novel dinucleotide mutation in keratin 10 in the annular epidermolytic ichthyosis variant of bullous congenital ichthyosiform erythroderma. J Invest Dermatol. 1997;108(3):357-361.
5.    Michael EJ, Schneiderman P, Grossman ME, Christiano AM. Epidermolytic hyperkeratosis with polycyclic psoriasiform plaques resulting from a mutation in the keratin 1 gene. Exp Dermatol. 1999;8(6):501-503.
6.    Virtanen M, Gedde-Dahl T, Jr., Mörk NJ, Leigh I, Bowden PE, Vahlquist A. Phenotypic/genotypic correlations in patients with epidermolytic hyperkeratosis and the effects of retinoid therapy on keratin expression. Acta Derm Venereol. 2001;81(3):163-170.}