S4C11VA3VisualAids

Whorled Transepidermal Elimination

(a basic reaction pattern, most characterisitc of EM-like reactions)

1. lysis and coagulation of basal keratinocytes

2. clustering of necrotic keratinocytes in epidermal defects

3. regeneration of keratinocytes of basal unit around clusters of necrotic keratinocytes

4. transfer of whorls of viable and necrotic keratinocytes into the superficial reactive unit of the epidermis

5. in the process of terminal differentitation, whorls and necrotic keratinocytes are eliminated at the surface, being delivered first to the superficial unit, and finally to the keratin layer

S4C11VA3-1: In an extension of the category of lichenoid lymphocytic vasculitis, the patterns in the category of erythema multiforme serve as a model. The basic features are listed in the above Table. These distinctive patterns define erythema multiforme, particularly the variant that is temporally sequenced with attacks of herpes simplex. The patterns, like those in lichen planus-like category, are best characterized as a common pathway, expressed in a variety of clinical settings. Some of the settings of the erythema multiforme complex include: 1.) toxic epidermal necrolysis, 2.) incontinentia pigmenti, 3.) herpes virus infection, and 4.) fixed drug eruption. Attention to the roof of vesicles in bullous pemphigoid will often reveal scattered markers that might be characterized as having erythema multiforme-like qualities. Subacute lupus erythematosus and graft vs host reaction share some of the features of an erythema multiforme-like reaction. In the erythema multiforme-like category, necrotic keratinocytes are nidi around which viable keratinocytes proliferate. The proliferating cells form whorls in the center of which the necrotic keratinocytes are clustered. Having reached the level of the superficial unit, the whorls and their necrotic keratinocytes (in concert with cells of the superficial unit of the epidermis) are carried upward; finally, they are discharged into the keratin layer. This toilet of the epidermis contrasts with that of a lesion of the lichen planus-like category. In the latter, lytic defects of the epidermal domain are inlaid with fibrous tissue; viable and necrotic cells of the defects are entrapped in the newly formed fibrous tissue. The fibrous inlay of a lesion of lichen planus constitutes an expansion of the dermal domain at the expense of the epidermal domain (accretive fibrosis). In erythema multiforme, regenerating keratinocytes cluster about the defects in the epidermal domain; they reduce the size of the defects; eventually, in their upward migrations, they and the necrotic cells are discharged along the skin surface. This observation would suggest that, in lichen planus, there routinely are disruptions of the basement membrane through which fibroblasts find their way into the lytic defects. In erythema multiforme-like processes, the basement membrane seems to retains its role as a barrier; fibroblasts are denied access to the defects. Both categories are lichenoid, but each is distinctive.

S4C11VA3-2: The concept of apoptosis has been much abused. Although critics are outspoken (and some of the most outspoken have no scientific background on which to base their criticisms), there is utility in the concept of programmed cell death . In the above drawing, TEE refers to transepidermal elimination of whorls of regenerating keratinocytes and entrapped necrotic keratinocytes. The upward-directed pathway in the drawing gives recognition to the whorled transepidermal elimination of the erythema multiforme complex. The downward directed pathway gives recognition to phenomena in the lichen planus-like category.

S4C11VA3-3: In this crude drawing, the epidermal insults of an erythema multiforme-like process are represented. They involve the basal unit of the epidermis and often are relatively confined to the actual basal layer (a single row of cells that sits upon the basement membrane). Regenerating keratinocytes fill in the defects; they, with entrapped inflammatory cells and necrotic keratinocytes, are carried to the surface; there they are discharged from the epidermis.

Whorled Transepidermal Elimination

(a reaction complex: a common pathway expressed in a variety of settings)

1. erythema multiforme

2. fixed drug eruption

3. toxic epidermal necrolysis

4. incontinentia pigmentii

5. subepidermal vesicular dermatitides (i.e., bullous pemphigoid, etc.)

S4C11VA3-4: In the above Table, members of a complex, defined on the basis of distinctive epidermal kinetics, are listed.

Lichenoid lymphocytic Vasculitis

(often additionally characterized by high component of histiocytes)

1. erythema multiforme (cell-rich at dermal-epidermal interface)

2. drug (especially fixed reactions) (cell-rich or cell-poor)

3. toxic epidermal necrolysis (cell-poor)

4. herpes virus infections (cell-rich)

5. lupus erythematosus (cell-poor)

6. dermatomyositis (cell-poor)

S4C11VA3-5: In the above Table, disorders, which might be cited as examples of the broad category of lichenoid lymphocytic vasculitides, are listed.

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