A fourth type of EB, known as Kindler syndrome, is classified as “mixed” because blisters may occur at any level: in the epidermis (intraepidermal), within the lamina lucida (junctional) and below the lamina densa (dermal).

Further classification of EB types depends on the mode of inheritance (dominant versus recessive); appearance and localization of blisters and erosions; and absence or presence and degree of severity of additional clinical features, such as nail dystrophy and involvement of internal organs such as the esophagus and trachea.

In general, it may be impossible to predict the subtype of EB in a newborn or infant suspected of having EB based on clinical features alone. Skin biopsy for electron microscopy and immunoepitope mapping are the first steps in the diagnosis of EB. These methods usually can suggest the subtype of EB. Immunoepitope mapping allows for more precise localization of the blister to the epidermis, dermal-epidermal junction or dermis, and may also allow for identification of the specific protein that is missing or present in reduced quantity.

Definitive diagnosis of the specific subtype of EB generally relies on genetic testing to identify confirmatory mutation(s) in one of the 10 genes associated with EB. In some patients , no genetic mutation can be identified, and it is possible that other genes also result in EB when mutated. In some cases, identification of the involved mutation(s) also can help to predict the severity of blistering and associated complications. As genetic researchers continue to study Epidermolysis Bullosa, more is learned about the disorder and associated findings.