The porphyrias.

The vesiculobullous porphyrias are a group of blistering diseases with systemic as well as cutaneous manifestations ranging from mild to disabling, secondary to endogenous photosensitizing porphyrins. The characteristic patterns of porphyrin accumulation in erythrocytes, plasma, urine, and feces are invaluable for differentiating the vesiculobullous porphyrias from other blistering diseases and from one another. Most importantly, these porphyrin profiles are essential for distinguishing the acute vesiculobullous porphyrias, HCP and VP, from PCT, which is not associated with acute attacks. This distinction may prevent the potentially fatal administration of porphyrinogenic drugs to patients with HCP or VP. Histopathology is not helpful in differentiating the vesiculobullous porphyrias, as all typically show subepidermal bullae. Avoidance of sun exposure and precipitating factors are the initial steps in both the prevention and treatment of these entities. In addition, more specific therapy may be indicated, as discussed in the preceding pages.