Epidermolysis bullosa (EB) is a group of hereditary disorders characterized by mechanical stress-induced blistering of the skin and mucous membranes. This article discusses the prevalence among and genetic studies of Japanese patients with EB.
Epidermolysis bullosa (EB) is a group of hereditary disorders characterized by mechanical stress-induced blistering of the skin and mucous membranes. EB is generally classified into the 3 main subtypes of EB simplex (EBS), junctional EB (JEB), and dystrophic EB (DEB), depending on the level of skin cleavage. According to the National EB Registry (USA), the prevalence of EB in the Unites States in terms of cases per million population is estimated to be 8.22 (EBS, 4.60; JEB, 0.44; dominant DEB [DDEB], 0.99; recessive DEB [RDEB], 0.92). The prevalence of EB in Japan in terms of cases per million is estimated to be 4.03 to 5.16 (EBS, 1.54; JEB, 0.34; DDEB, 1.02; RDEB, 1.60), based on data from the Japanese Study Group for Rare Intractable Skin Diseases in 1994. However, the precise disease frequency of EB in Japan is still controversial.
Genetic studies of Japanese patients have revealed specific mutations and distinct tendencies in the genes responsible for the 3 EB subtypes. For example, the proportion of Japanese patients with EBS with KRT5 mutations is 3 times higher than those with KRT14 , whereas outside of Japan, mutations in these 2 genes have been reported as equally prevalent. In the LAMB3 gene, which is associated with JEB, the recurrent mutations R42X and R635X are more common among Caucasians than among ethnic Japanese. The mutations 5818delC, 6573+1G>C, E2857X, and Q2827X have been regarded as recurrent COL7A1 mutations associated with DEB in Japan.
The medical expenses at the hospital for patients with JEB and DEB are covered under the public expenditure system, and 333 JEB and DEB patients in Japan are certified to receive medical care. However, the expense of the dressings and bandages, which is necessary for EB care, is not covered, and the patients have to purchase all that they need. Guidelines for the diagnosis and treatment of EB have been drafted by the Japanese Study Group for Rare Intractable Skin Diseases. In March 2008, the Dystrophic Epidermolysis Bullosa Research Association (DebRA) of Japan was founded ( www.ne.jp/asahi/eb-japan/com/english1.html ), and more than 50 patients with EB and their families have been registered.
The environment surrounding patients with EB has been slowly improving, but support for such patients is still not sufficient (eg, the government finally begins moves to cover part of their dressing costs). EB patients, dermatologists, dermatologic researchers, and the government must interact more closely to improve the quality of life for these patients.