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Trait Profile




Epidermolysis Bullosa Simplex

Epidermolysis Bullosa describes a large group of genetic conditions that cause blistering of the skin after very little, or no injury. Epidermolysis Bullosa Simplex is caused by mutations in the KRT5 and KRT14 genes, each of which makes a keratin protein.

Characteristics of Epidermolysis Bullosa Simplex
Fragile skin characterizes all types of Epidermolysis Bullosa. Mutations in genes that code for proteins used to anchor skin layers cause all four main types of Epidermolysis Bullosa: Epidermolysis Bullosa Simplex (EBS), Dystrophic Epidermolysis Bullosa (DEB; see trait profile), Junctional Epidermolysis Bullosa (JEB; see trait profile), and Kindler syndrome. The type of Epidermolysis Bullosa depends on which layer of skin is affected. In EBS the epidermis, or outer-most layer is affected. In DEB, the lower dermis is affected. Junctional EB (JEB) causes fragility of the lamina lucida, the layer between the dermis and epidermis. Kindler syndrome is another very rare type of EB that affects all three layers. Epidermolysis Bullosa can appear very different between types, and between people with the same type.
In most cases of EBS, blisters or open areas without a layer of skin are seen at birth. However in milder cases, blisters may first develop on the hands and knees from crawling, or when a child learns to walk. The skin on the palms and soles of the feet may thicken and become tough, and nails may be misshapen or ridged. In some adults with EBS, blisters may form only in hot weather or with repetitive sports activities, like hiking. Infants may have blistering in the mouth, and have higher nutritional needs. In severe cases infants can die from EBS; more often skin strength gradually improves with age. EBS does not affect intellectual abilities. However, EBS can be emotionally, socially and financially difficult for families.

Diagnosis/Testing
A diagnosis of EBS can be made by a dermatologist by looking at a skin sample under an electron microscope. Diagnosis can be confirmed by genetic testing for a change or mutation in the KRT5 or KRT14 genes. These genes make the keratin 5 and keratin 14 proteins, respectively. These proteins help to provide strength to the outer layer of the skin. Mutations in either of these genes do not allow the protein to work normally, thus causing the features seen in EBS.

Management/Surveillance
Management of EBS varies by severity. The use of soft clothing and shoes may help minimize blisters or erosions. Newborns with EBS need special attention to diaper fastening, how they are held, and how they are carried in baby carriers. For instance, picking up a child with severe EBS under the arms may cause the skin to shear. Completely preventing blisters is not possible. Once they form, blisters should be lanced and drained to prevent them from becoming larger. Ointments for the skin, vinegar or small amounts of bleach in a bath, or oral antibiotics may be needed to prevent or heal infections. Bandaging helps shield open areas from infection and assist healing. Various non-adhesive dressings are available commercially to cover open wounds and provide padding. Band-Aids, hospital tape or other adhesives can tear the skin or cause blisters at the edges. In severe EBS, pain management needs to be addressed. Heat and humidity can worsen blistering or itching under bandages. Poorly fitted or rough shoes and clothing should be avoided when possible. Repetitive or high impact activities such as running or playing football can cause additional blistering in milder EBS. The level of acceptable activity will be different for each individual. Physical and occupational therapy are helpful to develop strength.

Mode of inheritance
EBS is inherited in autosomal dominant pattern. This means inheriting one mutation is enough for an individual to be affected and show signs of EBS. The mutation can be inherited from an affected parent or it can occur brand new (de novo) in an affected child.

Risk to family members
The risk to family members depends on whether or not the individual with EBS has a parent affected with EBS. If a parent also has EBS, the risk of having a child with EBS is 50% with each pregnancy. If a parent does not have EBS, the risk of other siblings being affected is very low.

Special considerations
None

Resources
Genetics Home Reference: Epidermolysis Bullosa Simplex
DebRA of America, Inc.
ebnurse
NIAMS: Epidermolysis Bullosa
EBCare Registry

References
Fine, J. (2010)."Inherited Epidermolysis Bullosa." Orphanet Journal of Rare Diseases 5:12
Intong, LRA. et al. (2012)."Inherited epidermolysis bullosa: New diagnostic criteria and classification." Clinics in Dermatology 30(1): 70-77.
Pfendner EG, Bruckner AL. (Updated 1 September 2011). Epidermolysis Bullosa Simplex. In: GeneReviews at GeneTests Medical Genetics Information Resource (database online). Copyright, University of Washington, Seattle. 1997-2013. Available at http://www.ncbi.nlm.nih.gov/books/NBK1369/. [Accessed 10/09/2013].

Created:10/2013

Updated:mm/yyyy

Created by:Michele Disco, MS, CGC

Edited by:Seema Jamal, MSc, LCGC



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