Kindler epidermolysis bullosa (or Kindler EB) is a rare type of epidermolysis bullosa, which is a group of genetic conditions that cause the skin to be very fragile and to blister easily.

From early infancy, people with Kindler EB have skin blistering, particularly on the backs of the hands and the tops of the feet. The blisters occur less frequently over time, although repeated blistering on the hands can cause scarring that fuses the skin between the fingers and between the toes. Affected individuals also develop thin, papery skin starting on the hands and feet and later affecting other parts of the body; changes in skin coloring; and small clusters of visible blood vessels just under the skin (telangiectases). This combination of features is known as poikiloderma. In some affected individuals, the skin on the palms of the hands and soles of the feet thickens and hardens (hyperkeratosis). Kindler EB can also cause people to be highly sensitive to ultraviolet (UV) rays from the sun and to sunburn easily.

Kindler EB can also affect the moist lining (mucosae) of the mouth, eyes, esophagus, intestines, genitals, and urinary system, causing these tissues to be very fragile and easily damaged. Affected individuals commonly develop severe gum disease that can lead to early tooth loss. The moist tissues that line the eyelids and the white part of the eyes (the conjunctiva) can become inflamed (conjunctivitis), and damage to the clear outer covering of the eye (the cornea) can affect vision. Narrowing (stenosis) of the esophagus, which is the tube that carries food from the mouth to the stomach, causes difficulty with swallowing that worsens over time. Some affected individuals develop health problems related to inflammation of the colon (colitis) or damage to the mucosa in the vagina, the anus, or the tube that carries urine from the bladder out of the body (the urethra).

Kindler EB increases the risk of developing a form of cancer called squamous cell carcinoma. This type of cancer arises from squamous cells, which are found in the outer layer of skin (the epidermis) and in the mucosae. In people with Kindler EB, squamous cell carcinoma occurs most often on the skin, lips, and the lining of the mouth (oral mucosa).

Kindler EB results from variants (also known as mutations) in the FERMT1 gene. This gene provides instructions for making a protein known as kindlin-1. This protein is found in epithelial cells, which are the cells that line the surfaces and cavities of the body. In the skin, kindlin-1 plays a critical role in specialized cells called keratinocytes, which are the major component of the epidermis. Kindlin-1 is involved in several important cell functions, including cell growth and division (proliferation), the attachment of cells to the underlying network of proteins and other molecules (cell-matrix adhesion), and the movement (migration) of cells.

Most variants in the FERMT1 gene prevent the production of any functional kindlin-1. A lack of this protein disrupts many essential cell functions. For example, keratinocytes without kindlin-1 have an abnormal structure and cannot grow or divide normally. They are also less able to attach the epidermis to the underlying layer of skin (the dermis). These changes make the skin fragile and prone to blistering. Similarly, a lack of kindlin-1 in epithelial cells of the mucosae causes damage that makes these tissues extremely fragile. It is unclear how a shortage of kindlin-1 is related to squamous cell carcinoma in people with Kindler EB.

Normal Function

The FERMT1 gene provides instructions for making a protein called kindlin-1. This protein is found in epithelial cells, which are the cells that line the surfaces and cavities of the body. In the skin, kindlin-1 plays a critical role in specialized cells called keratinocytes, which are the major component of the outer layer of the skin (the epidermis).

Kindlin-1 is part of cell structures called focal adhesions. These structures contain many different kinds of proteins, which are involved in linking the cell's internal framework (the cytoskeleton) to the intricate lattice of proteins and other molecules that surrounds cells (the extracellular matrix). This linking is known as cell-matrix adhesion. Kindlin-1 attaches (binds) to and turns on (activates) proteins called integrins, which directly connect the cytoskeleton with the extracellular matrix and help transmit chemical signals into the cell.

As part of focal adhesions, Kindlin-1 is involved in several important cell functions, including cell growth and division (proliferation) and the movement (migration) of cells.

Health Conditions Related to Genetic Changes

Kindler epidermolysis bullosa

More than 70 variants (also known as mutations) in the FERMT1 gene have been identified in people with Kindler epidermolysis bullosa (EB). This disorder is a rare type of epidermolysis bullosa, which is a group of genetic conditions that cause the skin to be very fragile and to blister easily. Kindler EB also affects the moist lining (mucosae) of the mouth, eyes, esophagus, intestines, genitals, and urinary system, causing these tissues to be very fragile. In addition, people with Kindler EB have an increased risk of developing a form of cancer called squamous cell carcinoma.

Most variants in the FERMT1 gene prevent the production of any functional kindlin-1. A lack of this protein disrupts many essential cell functions. For example, keratinocytes without kindlin-1 have an abnormal structure and cannot grow or divide normally. They are also less able to attach the epidermis to the underlying layer of skin (the dermis). These changes make the skin fragile and prone to blistering. Similarly, a lack of kindlin-1 in epithelial cells of the mucosae causes damage that makes these tissues extremely fragile. It is unclear how a shortage of kindlin-1 is related to squamous cell carcinoma in people with Kindler EB.

Other Names for This Gene

• C20orf42
• DTGCU2
• fermitin family homolog 1
• FLJ20116
• KIND1
• kindlerin
• kindlin 1
• kindlin syndrome protein
• unc-112-related protein 1
• UNC112 related protein 1
• UNC112A
• URP1

Genomic Location

• 25% chance to be affected
• 50% chance to be an unaffected carrier like each parent
• 25% chance to be unaffected and not a carrier

Currently there is no cure or established treatment for Kindler syndrome. Therefore, the goals of management are to treat the symptoms and prevent complications.

When possible, children with Kindler syndrome should be managed by a multidisciplinary team of specialists, which may include a dermatologist, ophthalmologist, dentist, gastroenterologist, urologist, and dietitian. This is best achieved in a center with experience in caring for children with skin fragility.

Skin care may include standard blister care; using moisturizers; and avoiding skin trauma and sun exposure. Mucosal involvement may require lubrication of the cornea; regular dental care for optimal oral hygiene to reduce periodontal disease; and management of gastrointestinal and urethral complications.

Cancer screening should begin in adolescence and be repeated annually. This may include screening for pre-malignant keratoses and early squamous cell carcinomas.

Kindler EB appears to be rare. About 250 cases have been reported worldwide.