S6C18P12-Subepidermal Vesicular Dermatitis

S6C18P12-1:  With a reticulum stain, the basement membrane and the reticular fibers of the papillary dermis are demonstrated. The blue arrows point to areas in which the basement is well-preserved. The green arrows identify areas in which the basement membrane is faintly or poorly outlined. The latter areas are interpreted as zone of partial lysis of connective tissue fibers; the patterns in these areas suggest that damage to the connective tissue, particularly the basement membrane, may have had a role in initiating the bullous process. The two green arrows at the far right point to an area showing lysis of basement membrane. There is an ill-defined cleft at the dermal-epidermal interface; a basal layer is not defined in epidermis over this cleft. This change might suggest that, in addition to the partial lysis of basement membrane material, there has been cytolysis of basal keratinocytes. These two processes would account for the poor cohesion between epidermis and the dermis and for a separation at the interface (pemphigoid).

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S6C18P12-2: This is a nice demonstration of the cytopathic changes at the dermal-epidermal interface in an erythema multiforme-like process. To the left, defects have formed at the dermal-epidermal interface. Clearly, the phenomena in erythema multiforme-like processes are different from those of bullous pemphigoid, but both are, at least in part, diseases first manifested morphologically at the interface.

S6C18P12-3: In this area, the cytopathic changes in an erythema multiforme-like process have progressed to the formation of a subepidermal vesicle. Blue arrows identify clusters of necrotic (apoptotic) keratinocytes. Green arrows point to an area of cytolysis at the dermal-epidermal interface. A high component of eosinophils, as in this lesion, is a feature seen in the erythema multiforme-like changes of a lesion of incontinentia pigmenti, but does not exclude erythema multiforme.

S6C18P12-4: This lesion on the leg of a diabetic patient was presented at a seminar as an example of bullous diabetic dermopathy. In this example, the basement membrane appears to be on the floor of the vesicle. This clinical presentation probably is etiologically and pathogenetically heterogeneous. The reacting cells in the papillary dermis are histiocytes. There is focal evidence of lysis of basal keratinocytes.

S6C18P12-5: This is the margin of a subepidermal vesicle showing infiltrates of neutrophils, and a few histiocytes at the dermal-epidermal interface. There are small vacuoles on the dermal side of the basement membrane. There are a few  fragments of nuclear debris (early, or young, lesion of cicatricial pemphigoid). Focally, the sub-nuclear cytoplasm of basal keratinocyts is homogeneous and more acidophilic; the changes might be characterized as evidence of injury to basal keratinocytes.

S6C18P12-6: This is another example of the margin of a bullous lesion of cicatricial pemphigoid. There is a more intense infiltrate of neutrophils with a mixture of histiocytes. The radiating projections along the surface of a rete ridge to the left of the field may be remnants of partially digested dermal connective tissue.

S6C18P12-7: This is a third example of a lesion of cicatricial pemphigoid with attention to the patterns along the floor of a bulla. The arrows identify the surface of a partially preserved dermal papilla. Much of the fibrillary material, that is admixed among neutrophils, is interpreted as a meshwork of fibrin. In turn, there has been a reduction in the density of the fibrous matrix. A vessel extends close to the region of the exudate. The process is fibrolytic; this lysis of connective tissue is a harbinger of the sclerotic phase of this disease; one is a requisite to which the other is a reaction.

 

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