Epidermolysis bullosa simplex 1D, generalized, intermediate or severe, autosomal recessiveQ82.8

Autosomal recessive, moderate or severe, monogenic epidermolysis bullosa simplex-1D (EBS1D) with mutation in KRT14 (gene locus:: 17q21.2), is a skin disease characterized by traumatic blistering that usually resolves without scarring or with mildly atrophic scars. The severity varies; in some patients, the disease occurs locally with preferential involvement of the hands and feet. In others, the blistering may be generalized. In some patients, the condition improves with age.

This is due to a biallelic mutation in the KRT14 gene (gene locus: 17q21.2), which leads to a premature termination of translation and thus to the absence of expression of the encoded protein keratin 14.

Hovnanian et al (1993) reported a consanguineous French family in which two siblings had a recessive form of localized EBS and a mutation in the KRT14 gene. Both suffered from recurrent painful blistering of the lateral, dorsal, and plantar portions of the feet since early childhood. The blistering worsened in summer. These occurred as early as after walking or after trivial minor trauma. Occasionally, blisters also appeared on the legs and thighs (e.g., after horseback riding). Palms and other parts of the body were spared from blister formation. Slightly atrophic scars were found on the feet. Hair, nails, teeth, and oral mucosa were normal. No milia were found; no palmoplantar atoses. The disease did not improve with age.

Rugg et al (1994) reported a child with severe generalized epidermal blistering that began three days after birth and had a homozygous mutation in the KRT14 gene. The blistering occurred virtually everywhere on the body, including the arms, legs, trunk, face, scalp, and oral mucosa. Anterior teeth were discolored and showed enamel defects. Fingernails were ridged and of uneven thickness. The tendency to blister decreased with age.

Chan et al (1994) studied a patient with severe autosomal recessive EBS who had a homozygous mutation in the KRT14 gene. Blistering of the hands and feet was evident at birth. Later, generalized blistering occurred, which was particularly pronounced on the hands and face. The blisters healed without scarring.

Jonkman et al (1996) studied 2 closely related Dutch families with 4 members with congenital skin blistering and homozygous mutation in KRT14. The patients were all adults (age range 34 to 74 years) who had suffered from severe generalized blistering after trivial trauma since birth. There was a slight improvement with increasing age. The mucous membranes of the mouth, nose, and genitals were occasionally mildly affected. The esophagus and eyes were not affected. The lesions healed without scarring.

Histology shows cleavage at the basal keratinocyte level (Hovnanian et al. 1993; Jonkman et al.1996).

EM: Electron microscopic examination of the skin showed cleavage within basal keratinocytes and no clumping of tonofilaments (Hovnanian et al. 1993).

IF: No evidence of KRT14 in the skin (Chan et al. 1994).

1. Chan Y et al. (1994) A human keratin 14 'knockout': the absence of K14 leads to severe epidermolysis bullosa simplex and a function for an intermediate filament protein. Genes Dev 8: 2574-2587.
2. Fine JD et al (2008) The classification of inherited epidermolysis bullosa (EB): report of the Third International Consensus Meeting on diagnosis and classification of EB. J Am Acad Derm 58: 931-950.
3. Hovnanian A et al (1993) A missense mutation in the rod domain of keratin 14 associated with recessive epidermolysis bullosa simplex. Nature Genet 3: 327-331.
4. Jonkman MF et al (1996) Effects of keratin 14 ablation on the clinical and cellular phenotype in a kindred with recessive epidermolysis bullosa simplex. J Invest Derm 107: 764-769.
5. Rugg EL et al (1994) A functional 'knockout' of human keratin 14. Genes Dev.8: 2563-2573.