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Autosomal dominant epidermolytic ichthyosis
Epidermolytic ichthyosis (EI) is a rare keratinopathic ichthyosis (KPI; see this term), that is characterized by a blistering phenotype at birth which progressively becomes hyperkeratotic.
ORPHA:312Classification level: Disorder
- Bullous congenital ichthyosiform erythroderma
- Bullous congenital ichthyosiform erythroderma of Brock
- Bullous ichthyosis
- Epidermolytic hyperkeratosis
- Ichthyosis hystrix Brocq type
- Prevalence: 1-9 / 1 000 000
- Inheritance: Autosomal dominant
- Age of onset: Neonatal
- ICD-10: Q80.3
- OMIM: 113800 607602
- UMLS: C0079153
- MeSH: -
- GARD: 1039
- MedDRA: -
The prevalence of all types of KPI is estimated at 1/ 909,000 in France. The exact prevalence of EI is unknown.
Infants present at birth, or shortly after, with generalized erythroderma, severe blistering, mild scaling, and superficial skin erosions at sites of minor trauma and flexural areas. Yellow-brown hyperkeratotic plaques, often associated with mild background erythroderma, develop later, usually in the first months of life. Over time, hyperkeratosis worsens and blister formation decreases but may still occur (following skin trauma or during summer). Hyperkeratosis is most often generalized but some patients have limited skin lesions, especially on joint flexures, anterior neck, abdominal wall, and infragluteal folds. Palmoplantar involvement is seen in some patients. Skin is often itchy and smelly, and skin infection may occur. Other features may include hypohidrosis, scalp scaling and nail dystrophy. Growth failure may be seen in severe cases. EI persists into adulthood, with hyperkeratosis of variable intensity and extension. A clinical variant of EI, annular EI (see this term), shows an annular distribution of polycyclic erythematous scales that generally develop on the trunk and extremities and that tend to resolve.
The disease is caused by mutations in the genes coding for epidermal suprabasal keratins 1 (KRT1; 12q13.13) and 10 (KRT10; 17q21-q23), that impair keratin intermediate filament formation in the suprabasal keratinocytes. A genotype-phenotype correlation exists, with palmoplantar involvement being generally associated with KRT1 mutations. The position of the mutation may influence the severity of the phenotype.
Diagnosis is based on the clinical picture and on histological examination of skin lesion biopsies showing hyperkeratosis with orthokeratosis, hypergranulosis, and cytolysis in the upper stratum spinosum and granular layers (epidermolytic hyperkeratosis). Electron microscopy shows suprabasal keratinocytes with irregularly shaped keratin intermediate filaments clumps. Genetic testing confirms the diagnosis.
At birth, differential diagnosis includes toxic epidermal necrolysis, inherited epidermolysis bullosa, incontinentia pigmenti or herpetic infection, while in later stages it includes other KPIs such as superficial EI and ichthyosis hystrix of Curth Macklin (see these terms).
Genetic antenatal diagnosis is available.
Most cases are sporadic. The rest are autosomal dominant cases, more rarely autosomal recessive. Genetic counseling should be offered to affected families.
Management and treatment
Treatment is symptomatic. Emollients are often used but their efficacy is limited. Topical keratolytics or oral acitretin for severe forms can improve hyperkeratotic lesions, but are associated with adverse effects such as skin fragility and worsening of blistering. Antiseptic washes reduce the bacterial colonization and body odor. Antibiotic therapy is required in cases of bacterial infection.
The severity of the disease is variable. EI can impact the quality of life and may cause social handicap due to the skin's aspect, pain, pruritus, body odor, and/or recurrent infections. EI can also be life-threatening during the neonatal period due to infections and/or dehydratation.
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