Pretibial Dystrophic Epidermolysis Bullosa

Pretibial dystrophic epidermolysis bullosa is a rare subtype of dystrophic epidermolysis bullosa (DEB, see this term) characterized by the development of blisters, erosions, and lichenoid lesions predominantly in the pretibial region.

Epidemiology

Prevalence is unknown. Approximately 40 families or sporadic cases have been reported to date.

Clinical description

The disease usually manifests at birth or during infancy, but may also be delayed until the adolescence. It involves almost exclusively the anterior lower legs (pretibial areas and feet), the hands and nails. Individual lesions, which tend to be papular or plaque-like, are often violaceous, suggesting the clinical diagnosis of lichen planus. Some patients complain of pruritus. Healing of blisters is associated with hypertrophic scarring and milia formation. Dystrophy of both fingernails and toenails is characteristic. Unlike in lichen planus, these nail changes do not include pterygium formation.

Etiology

Pretibial DEB is caused by mutations within the type VII collagen gene (COL7A1). Mutations in this gene lead to an alteration of function or to reduced amounts of collagen VII. This impairs collagen VII assembly into anchoring fibrils which anchor the basement membrane to the underlying dermis. This in turn causes reduced skin resistance to minor trauma.

Genetic counseling

The disease follows an autosomal dominant (pretibial DDEB) or an autosomal recessive (pretibial RDEB) pattern of inheritance.