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Lichen Sclerosis et Atrophicus
The collagenous matrix of the papillary dermis clearly is different from the coarse fibrous mat of the reticular
dermis. These differences are in large part an adaptation in which the delicate matrix of the papillary dermis facilitates the delivery of nutrients to, and the removal of metabolites from, the epidermis. In
accommodating the needs of the epidermis, the papillary dermis functions as stroma. Stroma is a specialized mesenchyme; it most distinctive in those sites in which stroma supports an epithelial component.
The reticular dermis is a tough, resilient mat. It provides the physical integrity of the skin, but is
ill-suited for the direct support of epithelium. It may be that some of its fibrous components are even injurious, if the fibrous component makes direct contact with epithelium. The elastic fibers of the reticular
dermis are chemically different from those of the papillary dermis. Evidence of the differences are found in the staining characteristics of elastica in the two sites; those of the reticular dermis are PTAH(+). In
searching for a possible role of “abnormal,” chemically distinctive elastic fibers (having the tinctorial qualities of those of the reticular dermis, but in the papillary dermis near the dermal-epidermal interface)
in eliciting the reaction we speak of as elastosis perforans serpiginosa, the possibility that these PTAH(+) elastic fibers are injurious, or ecotaxically attractive to epithelium should be considered. Normal
papillary dermis contains delicate, arborizing elastic fibers that are PTAH(-). The distinctions between the two anatomic forms of dermal connective tissue reinforce the notion that the papillary dermis is specially
adapted to support epithelium.
(NOTE: The papillary dermis also provides a pliable interface; if epithelium sat solely, and directly, on the
reticular dermis, abrasions would be more common. Even in disease, the distinctions between papillary dermis and reticular dermis usually are preserved. In the repair of a neurotic excoriation (and even a
shave biopsy), regenerating squamous epithelium may be found in direct contact with connective tissue of the reticular dermis; connective tissue fibers may even be found in this epithelium among the keratinocytes.
Lichen sclerosis et atrophicus is a disease that initially affects stroma (i.e., papillary dermis), particularly
at its interface with the epidermis on one side
and with the reticular dermis on the other. In early lesions, the process apparently begins at the dermal-epidermal interface. It is appropriate to characterize the early epidermal response at the dermal-epidermal interface as a lichenoid reaction. The process seems to begin at the dermal-epidermal interface; the early expressions of fibrosis sometimes seem to be closely related to the zone of the basement membrane.
The epidermis of a lesion of LS&A may be hyperplastic, but often shows some degree of atrophy (S9C17P9-1 & 2). Prominent degrees of hyperplasia seem to be more common in genital forms of LS&A. Liquefaction degeneration at
the dermal-epidermal interface, and erosion of the rete ridges are features of fully developed lesions (S9C17P9-2). In early lesions,
the basal unit may be hyperplastic and there may be lytic defects at the dermal-epidermal interface (S9C19P11-1 & 2). Colloid bodies
may be found in the stroma, near the dermal-epidermal interface (S9C17P9-2 & 4). The product of the sclerosing reaction, in a classic lesion, is a delicate, rather acellular, hyaline matrix; it first makes its
appearance in juxta-position to the basement membrane zone (S9C17P9-5). The relationships are such that one might predict that the
matrix has basement membrane qualities.
In fully developed lesions, the peculiar fibrosing process results in the formation of a delicate, often
edematous hyaline matrix; it is relatively acellular. The infiltrates of inflammatory cells may be situated at the dermal-epidermal interface in an early lesion. In older lesions, the infiltrates tend to be confined
at the interface between the delicate hyaline matrix and the reticular dermis (S9C17P9-1-3). The fibrosing reaction extends into the
reticular dermis among collagen bundles (lymphohistiocytic collagenosis). The alterations in this portion of the lesion resemble those of superficial morphea (S9C18P10-1-4). Plasma cells often are a feature of the infiltrates of superficial morphea (S9C18P10-5); they are fairly common in the infiltrates of LS&A.
Oliver GF, Winkelmann RK, Muller SA: Lichenoid dermatitis: a clinicopathologic and immunopathologic review of
sixty-two cases. J Am Acad Dermatol 1989;21: 284-92.
Radiodermatitis
Radiodermatitis is another disorder in which sclerosis may significantly alter the quality of the fibrous mats
of the dermis; it may obliterate the morphologic distinctions between reticular dermis
and papillary dermis. In such lesions, the epidermis may be atrophic, or hyperplastic. The changes may be complicated by a premalignant keratinocytic dysplasia. Ulcerations are common. Vacuolar changes are common at the dermal-epidermal interface. The basement membrane may be thickened and hyalinized (S9C19P11-3)
For some examples, the changes in the epidermis and the upper portion of the dermis may resemble those of
a lesion of LS&A (S9C19P11-3-6). The dermis may be fibrotic, hyalinized, and edematous. Elastosis of “actinic” type is a common
feature. Telangiectasia is a common feature and, focally, the vessels may be dilated to the point that the designation, capillary aneurysm, might have application. Vessels may show thickened, hyalinized walls.
Thrombosis of small, superficial vessels is a common feature. Foam cells often collect the subendothelial area. Fibroblasts often are hypertrophied (they tend to be stellate in outline) and, in some examples, show
nuclear atypia; the atypical nuclei vary in size, outline, and in density of chromatin. Some of the large, atypical nuclei show smudgy chromatin patterns.
Acrosclerosis
The histologic diagnosis of acrosclerosis, particularly in the setting of Raynaud’s disease, is difficult. The
changes often are subtle. They only minimally resemble those of a fully developed lesion of morphea. An evaluation of the changes in the reticular dermis is complicated by the anatomy of the site; broad, fibrous
retinacula normally extend in the subcutaneous fat to the lower margin of the dermis in the sites affected by acrosclerosis. An alteration in the character, and quality, of the fibrous tissue at the interface
between the reticular dermis
and the fat may be a clue to the presence of an abnormal sclerosing process. The reticular dermis in these acral sites also is somewhat different. Criteria need to be modified in the evaluation of the pattern of collagen bundles. Small vessels in this site also tend to have thickened walls but, in acrosclerosis, these vascular changes perhaps are accentuated (S9C20P12-1-4).
Vayssairat M, Baudot N, Gaitz JP: Raynaud’s phenomenon together with antinuclear antibodies: a common subset of
incomplete connective tissue disease. J Am Acad Dermatol 1995:32: 747-9).
Hypertrophic Fibroplasia with Pruritus
(Lichen Simplex Chronicus and Prurigo Nodularis)
Inflammatory disorders of the reactive superficial unit of the skin often are pruritic. Certain sensitive
individuals, in their response to the pruritus, may react in a distinctive, hypertrophic manner; either the response has psoriasiform qualities, with distinctive patterns of papillary dermal fibrosis, or it
is predominantly a fibrosing process affecting both the papillary dermis, and the reticular dermis. The latter examples are characterized by the formation of a plaque or nodule (S9C21P13-1). That the two phenomena may be manifested in a single patient suggests that the events are closely, perhaps sequentially,
related.
Lichen simplex chronicus is a hypertrophic, psoriasiform dermatitis. The epidermis shows regular elongation of
the rete ridges with hyperkeratosis and parakeratosis. Spongiosis may be a feature. The papillary dermis is widened and fibrotic. Perivenular infiltrates of lymphoid cells extend upward from the upper portion
of the reticular dermis along vessels into the papillary dermis and the dermal papillae; they may extend into the epidermis in sites of spongiosis.
The patterns of fibrosis along the perimeters of the elongated dermal papillae are distinctive (not diagnostic -
they are a manifestation of a basic reaction to injury). Fibrous lamellae outline the rete ridges; the number of lamellae along a single rete ridge is proportional to the chronicity of the process (S9C21P13-2 & 3).
In prurigo nodularis, fibrosis in the upper portion of the dermis is localized; it acquires tumoral qualities (S9C21P13-4). The epidermis over well-developed lesions shows effacement of rete ridges; it may be separated from the dermal component
by a cleft. Fibrin often is deposited along the surface of the cleft. In the nodule, the patterns of collagen bundles are altered. Perivascular infiltrates of lymphoid cells often are prominent. Often, there is an
increased prominence of small nerves in the altered dermis. These nerves also are hyperplastic; they are individually enlarged and show Schwann cell hyperplasia (on viewing related material, I think of a young Lloyd
Elmer [Reed RJ, and Elmer LC: Multiple acral fibrokeratomas: a variant of prurigo nodularis. Arch Dermatol 1971; 103:286-297).
Connective Tissue Nevus
In the category of collagenoses, the connective tissue nevi are distinguished by fibroplasia without an
accompanying inflammatory component. In addition, the alterations in the patterns of collagen bundles of the reticular dermis are only subtlely distorted (S9C21P13-5 & 6). The vertical dimensions of the dermis may be increased within the lesion, but this is not always a prominent
feature. Some examples are associated with a reduced amount of elastica. Some show no significant alterations in elastica. Some are associated with an increased amount of elastica. In the latter category, the
elastic fibers are coarse; they often are aligned in a lattice-like pattern among individual collagen bundles of the reticular dermis. With a proper Verhoef-van Giesen stain, the coarse, black elastic fibers are
outlined by an irregular sheath of pale yellow material (pre-elastin); such fibers on an H&E stain appear to have a “bushy” quality along their surfaces.
As an aside, elastosis perforans serpiginosis shows hyperelastosis of the upper portion of the dermis, including
the papillary dermis. The elastica is of reticular dermal type (PTAH +); it extends to the dermal-epidermal interface. The inflammation and “perforation,” that characterize a lesion of elastosis perforans
might be a response to ectopic elastica in close proximity to epithelium (i.e., elastica of reticular dermal type in an abnormal location). From this perspective, elastosis perforans is a connective tissue nevus, in
which the elastica of the papillary dermis has abnormal qualities. In contact with the epidermis, this type of elastica may evoke an inflammatory response and invasive growth of epithelium down into the dermis.
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