EB Simplex

2 EB Simplex
2.1 What is the Cause of EB Simplex?
2.2 How is EB Simplex Inherited?
2.3 Weber-Cockayne Subtype of EB Simplex or EBS-WC
2.4 Koebner Subtype of EB Simplex or EBS-K
2.5 Dowling Meara Subtype of EB Simplex or EBS-DM
2.6 Common Manifestations of EB Simplex
2.7 Uncommon Manifestations of EB Simplex
2.8 Rare Manifestations of EB Simplex
2.9 Other Subtypes of EB Simplex

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2.1 What is the cause of EB Simplex?

Through research it is now known that the genes that carry the instructions necessary to produce the proteins in the top layer (keratins) are faulty. This results in incorrectly formed keratins, deeming them unable to perform their normal role as a 'scaffolding' for the top most layer of skin. It appears as though there is a mutation (a change in the genetic material) within Keratin genes K5 or its partner K14. So as a result, the top layer of skin falls apart, resulting in a blister. Although EB Simplex is considered a non-scarring form of EB, secondary infection may cause scarring.

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2.2 How is EB Simplex Inherited?

EB Simplex is usually inherited as an autosomal dominant condition. One parent of an affected person will usually also have the condition, though it is possible for EB simplex to appear 'sporadically' (to appear for the first time in a person who has no other affected family member). Anyone who has EB simplex whether male or female, can pass the condition on to his or her children. Each time a pregnancy occurs, there is a 1 in 2 chance that the child will inherit EB simplex.

Some precipitating factors that may cause an outbreak of blistering may include the following:

  • Physical stress
  • Emotional stress
  • Warmer climates
  • Infections
  • Sexual maturation

Even though some forms of EB Simplex are localized it is important to know that all skin cells are affected. Therefore, all skin surfaces are prone to develop generalized blistering.

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2.3 Weber-Cockayne Subtype of EB Simplex

This form is also termed localized EB simplex. This disorder usually presents in childhood or adolescence. It may also occur in an infant or adult life. In many instances it presents itself in infancy from friction induced by shoes and starting to walk.

People with Weber Cockayne EB Simplex develop blisters on their feet and hands, (usually palms and soles) in response to friction. These wounds usually heal without scarring. Walking even short distances is often enough to cause blisters. They may experience thickening of the skin (keratoderma) on the soles of the feet. This type of EBS usually does not involve nails or mucous membranes. Most individuals seem to be more prone to blisters in warmer climates and during periods of strenuous activity such as jogging, marching or walking. With trauma or friction rarely the blistering can be (generalized) or appear on other parts of the body.

Mutations are in the genes encoding K5 or K14.

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2.4 Koebner Subtype of EB Simplex

This is a form of generalized EB simplex. This disorder usually presents at birth or infancy. Blisters are noted to be widespread over the body's surface. Though it is not a common feature of this type of EB to scar on rare occasions it does happen. There may be mild involvement of mucous membranes. Fingernails and toenails are sometimes involved. Localized thickening of the skin (keratoderma) on the soles of the feet and the palms of the hands may occur especially as one gets older.

Mutations are in the genes encoding K5 or K14.

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2.5 Dowling Meara Subtype of EB Simplex

EBS-DM is a generalized form of EB simplex. This type of EB is probably the most severe form of EB Simplex.

Infants are often born with widespread grouping of blisters on the face, trunk and limbs. Blisters on hands and feet often eventually cause confluent keratoderma (thickening of the skin). In many cases these calluses form complete thickening of the palms and soles. If the thickening is severe enough it may limit the range of motion of a joint. In such cases, consultation from a surgeon may be necessary to determine the best course of treatment.

Heat may exacerbate blistering. Milia (tiny cysts on skin) may be present after blisters have healed. Nail thickening and discoloration is a common feature.

Blistering in Dowling Meara EBS can involve organs including the oral cavity, gastrointestinal tract and rarely, the upper respiratory tree.

Electron microscopy shows clumps of keratin filaments, which are not seen in other forms of EB simplex.

Mutations are usually in the genes encoding K5 or K14.

Since EBS-DM is the most severe form of EBS, the widespread blistering may lead to death in infancy. However, blistering tends to become smaller and less problematic for most patients as they grow older.

Since EB varies in severity these manifestations may or may not be experienced by the individual affected.

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2.6 Common Manifestations of EBS

  • Blisters
  • Keratoderma - Thickened skin on palms of hands and soles of feet. Confluent keratoderma in EBS-DM.
  • Nail dystrophy - The presence of rough, thickened or absent finger or toenails.
  • Problems with the soft tissue inside the mouth.

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2.7 Uncommon Manifestations of EBS:
  • Milia - Tiny skin cysts.
  • Atrophic scarring - Depressions in skin as a result of thinning in epidermis or dermis.
  • Anemia - A reduced amount of red blood cells, volume of red blood cells, amount of hemoglobin. Hemoglobin is the oxygen carrying portion of the red blood cell. The heme aspect of hemoglobin, is the iron compound that makes up the pigment part of the hemoglobin molecule. Anemia is more common in the severely affected individual.
  • Growth retardation. This is more common in a severely affected individual.
  • Gastrointestinal tract - Involvement of the GI tract may include blisters in mouth, esophagus and/or anal margins.

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2.8 Rare Manifestations of EBS:
  • Granulation tissue - The appearance of red fleshy tissue which is capillary formation during tissue healing This would be a rare occurrence in a person affected with EBS. This is more commonly seen in a person severely affected with Junctional EB.
  • Dental caries (cavities) - This is more common in people affected with RDEB or JEB however, if mouth care is not performed regularly it will increase chances of cavities.
  • Ocular (eye) involvement is more commonly seen in people with RDEB or JEB however, it has been reported in some forms of EBS.
  • Pseudosyndactyly - Fusion of fingers and/or toes. This manifestation is more commonly seen in RDEB. In rare instances it has been reported in EBS-DM.
  • Enamel hypoplasia - Underdeveloped enamel upon the teeth. This is more prevalent in patients with JEB.
  • Respiratory tract involvement. Rare occurrences have been noted in the more severely affected individual.
  • Genitourinary tract involvement. Rare occurrences involving the GU tract have been reported in some forms of EBS.

There is no evidence that people with EBS are at a higher risk for developing squamous cell carcinoma or malignant melanoma, however, suspicious wounds/lesions should always be evaluated by your dermatologist.

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2.9 Other Subtypes of EB Simplex

EB Simplex Superficialis, EB Simplex with Mottled Pigmentation and KallinÂ’s Syndrome.

There is a recessively inherited simplex that accompanies Muscular Dystrophy which appears to be a mutation in the Plectin gene.

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You may contact Debra of America with questions or concerns:

(212) 868-1573
staff [at] Debra [dot] org
www.Debra.org

*Please note that all medical information given by Debra is for informational purposes only. Our information is not intended to substitute the care and guidance given by a qualified physician. All regimens of care should be discussed with the patient's physician. Always check with your physician prior to starting any medications or treatment regimens.

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Other In Depth Topics

1 About EB
2 EB Simplex
3 Junctional EB
4 Dystrophic EB
5 Wound Care
6 Various Wound Care Products
7 Other Healthcare Problems
8 Bibliography

Related Information/Links
Understanding EB
Frequently Asked Questions
What is EB?
Family Stories
Medical Research