Figure 4-6. Vesicle/Bulla.
(8) Bulla (see figure 4-6). A fluid-filled elevation greater than 0.5 cm in
diameter (a burn blister).
(9) Pustule (see figure 4-7). A pus-filled lesion, which may have resulted
from infection of vesicles or bullae and may have had many forms and origins.
Figure 4-7. Pustule.
b. Secondary Lesions. These are the result of, or completion of, a primary
lesion. This can be caused by natural evolution of primary lesions (a vesicle bursts,
leaving an eroded area), or from the patients' manipulation of the primary lesion
(scratching a vesicle, leaving an eroded or ulcerated area).
(1) Crust (see figure 4-8). A dried residue of serous fluid, blood, or pus
overlying an area of lost or damaged epidermis. Crusting is the result in a wide variety
of inflammatory and infectious diseases.
Figure 4-8. Crust.