Laboratory Studies
Obtain a skin biopsy following a thorough history and physical examination. Routine histologic analysis is useful only for excluding other causes of blistering. When epidermolysis bullosa (EB) is suspected, the best approach is to obtain two biopsy specimens. Analyze one specimen using electron microscopy (EM) and the other using immunofluorescent microscopy.
Evaluate anemia using CBC count with iron studies in patients with severe epidermolysis bullosa, especially recessively inherited epidermolysis bullosa.
Evaluate infection using bacterial cultures from poorly healing wounds or wounds that appear infected.
Imaging Studies
Evaluate GI dysfunction. Esophageal strictures associated with junctional epidermolysis bullosa, dystrophic epidermolysis bullosa, or the pyloric atresia associated with a rare form of junctional epidermolysis bullosa can be visualized best by an upper GI series or endoscopy.
Other Tests
Evaluate nutrition using serum albumin, height and weight curves, diet diaries, and other analyses of nutrition and growth in patients with severe epidermolysis bullosa.
Evaluate contractures by establishing the range of motion of limbs and digits to monitor contractures and effectiveness of physical therapy.
Routine light microscopy can be used only to exclude other causes of blistering and cannot be used to make the diagnosis of epidermolysis bullosa.
Procedures
Electron microscopy
Obtain a biopsy specimen from a fresh blister. The best way to obtain a fresh blister is to induce it in the office by gently rotating a pencil eraser back and forth over an area of skin until epidermal separation is appreciated. Perform the biopsy at the edge of the blister, sampling both unblistered and blistered skin. Place the specimen into the appropriate holding medium (check with the laboratory beforehand) and immediately send it for transmission EM. EM biopsy holding medium usually contains glutaraldehyde.
EM is the criterion standard for determining the level of blistering. EM can provide additional information on BMZ morphology that can be helpful in making the diagnosis. For example, intermediate filament clumping indicates Dowling-Meara epidermolysis bullosa simplex. Rudimentary hemidesmosomes often are found in junctional epidermolysis bullosa subtypes. Absent or altered anchoring fibrils often occur in dystrophic epidermolysis bullosa subtypes.
Immunofluorescent microscopy
This study can provide information on the level of the blistering. Obtain a biopsy specimen at the edge of a fresh blister for optimal results. Make arrangements with the laboratory before obtaining the specimen, and promptly send it for analysis. Zeus-holding medium is used widely for immunofluorescent microscopy.
Immunomapping with antibodies to a hemidesmosomal antigen (eg, BP230 obtained from sera of a patient with bullous pemphigus) and an antibody to a lamina densa protein (eg, type IV collagen) can distinguish epidermolysis bullosa simplex, junctional epidermolysis bullosa, and dystrophic epidermolysis bullosa. For example, in epidermolysis bullosa simplex, both antigens localize to the floor. In junctional epidermolysis bullosa, BP230 localizes to the roof of the blister, while type IV collagen localizes to the floor. In dystrophic epidermolysis bullosa, both antigens localize to the roof of the blister.
In addition to providing information about the level of the skin separation, immunofluorescent microscopy can be useful in providing an important clue regarding the underlying molecular defect. For example, the laboratory at Stanford University routinely examines biopsy specimens with a panel of antibodies against each of the antigens known to be affected in epidermolysis bullosa. Often, a specific absence of staining with a particular antibody indicates the specific molecular defect. Often, in milder disease subtypes and in dominant disease subtypes, alterations in expression of affected proteins may be too subtle to appreciate, and further tests are required. A diagram of the dermal epidermal basement membrane and level of disruption in epidermolysis bullosa subtypes is shown in the image below.
Diagram illustrating the organization of the dermal epidermal basement membrane and level of disruption in epidermolysis bullosa subtypes. EBS: epidermolysis bullosa simplex. JEB: junctional epidermolysis bullosa. DEB: dystrophic epidermolysis bullosa.
DNA mutation analysis
Perform mutation analysis after immunofluorescent microscopy. This is the final step in elucidating the underlying molecular defect, and in most cases, it reduces the number of genes to be screened. DNA is extracted from blood of the patient and family members. Initial mutation screening is performed by restriction fragment-length polymorphism analysis, hotspot analysis, and finally, direct DNA sequencing.
Prenatal diagnosis [14, 15, 16, 17]
Once the mutations are identified in a family, reliable prenatal diagnosis is possible. DNA for prenatal diagnosis can be obtained as a chorionic villi sample as early as the ninth week of gestation. Alternatively, amniotic fluid drawn after the eleventh week can provide the necessary DNA. Schedule the procedure in close conjunction with the diagnostic laboratory that will receive the sample.
Those interested in genetic analysis of epidermolysis bullosa patients should contact GeneDx.
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Epidermolysis bullosa simplex localized (formerly termed Weber-Cockayne subtype). This mild bullous disease is characterized by localized blistering at sites of trauma such as the feet.
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Epidermolysis bullosa simplex, generalized (formerly termed Koebner subtype). Palmoplantar blistering and hyperkeratosis are noted.
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Epidermolysis bullosa simplex, generalized (formerly termed Koebner subtype). Close-up image shows hyperkeratotic papules and plaques on the palm.
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Junctional epidermolysis bullosa, generalized severe (formerly termed Herlitz or letalis) subtype. This severe disease is characterized by generalized intralamina lucida blistering at birth, significant internal involvement, and a poor prognosis.
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Dominantly inherited dystrophic epidermolysis bullosa. The blistering in this disease often is localized and is characterized by scarring and milia in healed blister sites.
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Dominantly inherited dystrophic epidermolysis bullosa. This subtype, similar to other dystrophic and junctional epidermolysis bullosa subtypes, can result in nail dystrophy and loss.
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Recessively inherited dystrophic epidermolysis bullosa pseudosyndactyly (mitten-hand deformity) of the hands and feet.
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Recessively inherited dystrophic epidermolysis bullosa; oral cavity blistering and scarring.
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Recessively inherited dystrophic epidermolysis bullosa; squamous cell carcinoma.
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Diagram illustrating the organization of the dermal epidermal basement membrane and level of disruption in epidermolysis bullosa subtypes. EBS: epidermolysis bullosa simplex. JEB: junctional epidermolysis bullosa. DEB: dystrophic epidermolysis bullosa.
