eMedicine Specialties > Dermatology > Pediatric Diseases

Epidermolytic Hyperkeratosis (Bullous Congenital Ichthyosiform Erythroderma)

Author: Sidney B Smith, MD, Medical Director, Dermatologist, Dermatology, Dermacare Laser and Skin Care Clinics of Tri-Cities
Coauthor(s): Jeffrey B Smith, MD, Mohs Surgery, Kaiser Permanente, San Jose, CA
Contributor Information and Disclosures

Updated: Jan 24, 2007

Introduction

Background

Epidermolytic hyperkeratosis (EHK) also is termed bullous congenital ichthyosiform erythroderma. EHK is a rare autosomal dominant ichthyosis, yet a high frequency of spontaneous mutations (up to 50%) occurs. In 1902, Brocq first described it as bullous ichthyotic erythroderma to distinguish the entity from congenital ichthyotic erythroderma.

Pathophysiology

The defect is found in the genes for keratin 1 and keratin 10.

Keratins are divided into 2 classes including basic type II keratins and acidic type I keratins. Keratin 1 is one of the basic type II keratins found on chromosome 12; keratin 10 is one of the acidic type I keratins found on chromosome 17.

Keratins form intermediate filaments when both type I and type II keratins are present. This combination provides structural stability to keratinocytes. Keratins 1 and 10 are coexpressed and are involved in the suprabasilar differentiation of keratinocytes. A defect at this level (as in EHK) weakens the structural stability of the keratinocytes, causing easy blistering, hyperproliferation, and hyperkeratosis.

Frequency

United States

One case per 200,000-300,000 persons

International

Same as in United States

Mortality/Morbidity

• Mortality is possible if sepsis or electrolyte imbalance is not treated properly during the neonatal period.
• Morbidities include recurrent infection, sepsis, and electrolyte imbalance, which are possible during the neonatal period.

Race

No racial predilection is apparent.

Sex

No sex predilection is recognized.

Age

EHK is a lifelong condition with an onset at birth or in the neonatal period.

Clinical

History

EHK presents at birth or shortly thereafter as erythema, blistering, and/or peeling, but symptoms in some patients may ameliorate over time.

Physical

In 1994, DiGiovanna and Bale separated the various clinical presentations of EHK into 2 primary types, including NPS (without severe palm/sole hyperkeratosis) and PS (with severe palm/sole hyperkeratosis) based on the presence or absence of severe palmoplantar hyperkeratosis. The 2 primary types were subdivided further into 3 subtypes each depending on the clinical presentations. Some of the subtypes have general involvement, while others are localized only.

• NPS subtypes do not have severe palmoplantar involvement. Distinctions between the 3 NPS subtypes are based on different clinical presentations.
  • NPS-1 has normal palmoplantar surfaces, no digital contractures, a hystrix scale, a generalized skin distribution, no history of erythroderma, a positive history of blistering, and patients may have abnormal gait.
  • NPS-2 is similar to NPS-1. The only differences are a brown scale instead of a hystrix scale and a lack of gait abnormalities.
  • NPS-3 has no palmoplantar hyperkeratosis, no digital contractures, and is generalized in skin distribution similar to NPS-1 and NPS-2. In contrast, the palmoplantar surface in NPS-3 is hyperlinear, has minimal scale, and a thin white scale is most prominent on the trunk. Erythroderma is mild to moderate. NPS-3 may have gait abnormalities similar to NPS-1.
• PS subtypes have severe palmoplantar involvement. The 3 subtypes are differentiated based on clinical presentations.
  • PS-1 has smooth palmoplantar hyperkeratotic surfaces, no digital contractures, a localized distribution of skin involvement (limited flexural involvement, truncal sparing), no erythroderma, a localized blistering, and no gait abnormalities.
  • PS-2 has smooth palmoplantar hyperkeratotic surfaces but has digital contractures, generalized skin involvement with hyperkeratosis most severe over the joints at both flexor and extensor surfaces, mild-to-moderate erythroderma, positive blistering, and may have gait abnormalities.
  • PS-3 has cerebriform palmoplantar surfaces, no digital contractures, a tan scale, generalized skin involvement, no erythroderma, neonatal blistering, and no gait abnormalities.

Causes

Defects in genes for keratin 1 and 10 are the cause of EHK. Defects in keratin 1 are associated with the PS variants; defects in keratin 10 are associated with the NPS variants.

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