| Epidermolysis bullosa simplex |
Epidermolysis bullosa simplex (EBS) is a disorder resulting from mutations in the genes encoding keratin 5 or keratin 14.[1] [2] It is one of the major forms of epidermolysis bullosa, a group of genetic conditions that cause the skin to be very fragile and to blister easily.[3]
EBS causes blister formation at the dermal-epidermal junction. Skin blisters easily, from even minor insults.
Epidermolysis bullosa simplex is caused by genetic mutations that prevent the proper formation of protein structures in the skin’s epidermis. The proteins of the outer epidermis do not bond properly with those of the inner dermis layer (dermal-epidermal junction). The affected genes, KRT5 and the KRT14, which are responsible for the creation of keratin 5 and keratin 14 proteins respectively, are tied to the four major types of epidermolysis bullosa simplex. However, a small number of epidermolysis bullosa simplex patients do not have mutations in their KRT5 and KRT14 genes. Mutations in the PLEC gene are also being researched, specifically in the gene’s role in the Ogna form of epidermolysis bullosa simplex. The PLEC gene is responsible for the formation of plectin, another skin protein that attaches the epidermis to the skin’s deeper layers.[4]
Epidermolysis bullosa simplex may be divided into multiple types:
| Type | Locus & Gene | OMIM | |
|---|---|---|---|
| Epidermolysis bullosa simplex with migratory circinate erythema | 12q13 (KRT5) | ||
| Epidermolysis bullosa simplex with mottled pigmentation. | 12q13 (KRT5) | ||
| Epidermolysis bullosa simplex, autosomal recessive | 17q12-q21 (KRT14) | ||
| Generalized epidermolysis bullosa simplex Also known as "Koebner variant of generalized epidermolysis bullosa simplex", presents at birth to early infancy with a predilection for the hands, feet, and extremities, and palmar-plantar hyperkeratosis and erosions may be present. | 17q12-q21 (KRT5), 12q13 (KRT14) | ||
| Localized epidermolysis bullosa simplex Also known as "Weber–Cockayne syndrome" and "Weber–Cockayne variant of generalized epidermolysis bullosa simplex", is characterized by onset in childhood or later in life, and is the most common variant of epidermolysis bullosa simplex. | 17q12-q21 (KRT5), 17q11-qter, 12q13 (KRT14) | ||
| Epidermolysis bullosa herpetiformis Also known as "Dowling-Meara epidermolysis bullosa simplex", presents at birth with a generalized distribution, often with oral mucosa involvement and variable lesions in infancy. | 17q12-q21 (KRT5), 12q13 (KRT14) | ||
| Epidermolysis bullosa simplex with muscular dystrophy A rare clinical entity, and is the only epidermolytic epidermolysis bullosa described that is not caused by a keratin mutation, presenting as a generalized intraepidermal blistering similar to the Koebner variant of generalized epidermolysis bullosa simplex, but also associated with adult onset muscular dystrophy. | 8q24 (PLEC1) | ||
| Epidermolysis bullosa simplex with pyloric atresia | 8q24 (PLEC1) | ||
| Epidermolysis bullosa simplex of Ogna Has onset in infancy, presenting with seasonal blistering on acral areas during summer months. | 8q24 (PLEC1) |