Diagnostic Hallmarks

1. Distribution: exposed areas, unilateral or asymmetrical location
2. History of specific trauma

Clinical Presentation

Traumatic bullae occur as a result of friction, thermal burns, or long-term constant pressure (”coma blisters”). A history of friction or burn is ordinarily apparent, but this history may not be given in cases of child abuse. Likewise, a useful, spontaneously given history is not often available in cases of coma blister. In these latter settings, the clinician has to first recognize that a unilateral or markedly asymmetric distribution suggests the possibility of external causation. Second, the clinician should appreciate that all of these traumatic blisters can arise either from normal-appearing skin or from an erythematous base. Finally, a directed history needs to be taken.

Friction blisters and coma blisters are generally round, whereas burn blisters are often elongated or linear, based on the nature of the thermal contactant. Coma blisters occur over bony prominences such as the posterior scalp (after prolonged operative anesthesia) or over the elbows, knees, or hips (coma secondary to drug overdose).

Course and Prognosis

Friction blisters rarely result in appreciable dermal damage, they heal quickly and without scarring. The same is often true for thermal and coma blisters, but deep dermal damage is possible in either situation. With deeper damage, ulcers rather than erosions are present when the blister roof is missing. Damage deeper than the papillary dermis is associated with scarring. Secondary infection can occur with traumatic blisters of all types, infection also favors the development of scarring.

Pathogenesis

Friction mechanically results in separation of the epidermis from the dermis, histologically, there is little that is distinctive. Second-degree thermal burns result in cytolysis of the epidermal cells. This gives a distinctive histologic biopsy pattern that can be very useful in evaluating suspected situations of child abuse. Blisters form during coma because of pressure ischemia, the first evidence of skin ischemia in most situations is the development of a blister. Some drug-associated overdosage and coma may also have a direct toxic effect on the sweat glands and other skin structures.

Therapy

Cool packs, if applied immediately, can decrease the likelihood of blister formation following second-degree burns. Blisters, once they occur, regardless of which traumatic insult, are best aspirated until flat. A bandage that offers sufficient compression to keep the blister roof in contact with the dermis should be applied immediately after aspiration. Surgical removal of the blister roof is appropriate if the blister roof is torn open, but the roof should not be removed if the blister is intact. A topical antibiotic such as mupirocin ointment can be used if the base of the blister is exposed. In general, erosions heal better if they are kept bandaged in spite of the age-old adage to keep all “sores” dry and exposed to the air.

This entry was posted on Friday, August 17th, 2007 at 10:27 am and is filed under Vesiculobullous Diseases. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.