The pictured lesion is an epidermal nevus, and pathology reveals epidermolysis and hyperkeratosis. The offspring of patients with an epidermal nevus that histologically demonstrates epidermolytic hyperkeratosis
are at increased risk of bullous congenital ichthyosiform erythroderma (BCIE).
Epidermolytic Hyperkeratosis (EHK), also known as BCIE, is an autosomal dominant (AD) genodermatosis
caused by KRT1 and KRT10 mutations, which are keratins expressed in the spinous and granular layers of the epidermis. BCIE presents at birth with widespread erythroderma and denuded skin. Over time, the skin becomes hyperkeratotic with deep ridges favoring the flexural surfaces and cobblestone appearing hyperkeratosis involving the extensor surfaces. Bacterial colonization of the skin can cause a distinctive odor. Histologic findings include dense hyperkeratotic orthokeratosis, acanthosis, hypergranulosis, and a distinct degeneration of suprabasal and granular layer keratinocytes which exhibit vacuolization and dense clumps of keratin. Small intraepidermal blisters may also be observed.
An epidermal nevus is a benign overgrowth of the epidermis that is generally congenital, but can also develop in childhood. They occur in ~ 1 to 3 out of 1,000 people and can present independently or as part of an inherited syndrome.
The offspring of patients who have an epidermal nevus of the epidermolytic hyperkeratosis type may develop generalized epidermolytic hyperkeratosis. In one study of patients with epidermal nevi of the epidermolytic hyperkeratosis type, point mutations in K10 were found in 50% of lesional cells. The same mutations were found in the offspring who developed
generalized epidermolytic hyperkeratosis. (
Paller et al. N Engl J Med 1994).
Non-Bullous CIE is an autosomal recessive (AR) disorder with various gene mutations
including: transglutaminase-1, 12R-lipoxygenase, and lipoxygenase-3. Newborns
have a collodion membrane. Following infancy, clinical findings include:
generalized erythroderma, diffuse fine scale, large plate-like scales on extensor
surfaces, possible palmoplantar keratoderma (PPK), hypohidrosis, cicatricial alopecia, ectropion, and eclabium.
Epidermolysis bullosa Dowling-Meara subtype is due to an autosomal dominant (AD) K5/K14
defect and leads to severe herpetiform generalized blistering and PPK.
Epidermolysis bullosa Non-Dowling-Meara subtype is also due
to an AD K5/K14 defect and leads to generalized blistering with variable
severity.
Clinical Pearl:
Offspring of patients with an epidermal nevus that histologically demonstrates
epidermolytic hyperkeratosis are at increased risk of BCIE (epidermolytic
hyperkeratosis).
