LUPUS ERYTHEMATOSUS (tier 2)

A thickened basement membrane is the most characteristic feature of a lesion of lupus erythematosus (S5C11P5-1-3, & S5C17P11-2). Coarse deposits at the basement membrane level are not always a prominent feature (S5C16P10-2). Perhaps the immunoglobulins, which are deposited at the dermal-epidermal interface, have a role in promoting the “transfer” of cells (perhaps a phenotypic transfer, as much as, or more than, a morphologic transfer) from the basal unit into the superficial unit (and, in turn, providing an explanation for the relative depletion of cells of the basal unit of the epidermis).

In lichenoid reactions, without attention to specific categories, there is a potential for the response of the epidermis to the immune assault to be an invasive hyperplasia (pseudoepitheliomatous hyperplasia). In the region showing invasive growth, hyalin deposits at the dermal-epidermal interface may be inconspicuous. Usually, with a careful search, focal areas, often at the periphery of the zone of hyperplasia, will show the characteristic changes of LE (if the background lesion is LE). Lesions of LE showing patterns of pseudoepitheliomatous hyperplasia qualify as hypertrophic forms (S5C11P5-4).

Dermal mucinosis is a common, and often a prominent, feature of the reticular dermis in lesions of LE (S5C12P6-3-4, & S5C15P9-1). The mucinous changes may be associated with an increase in the number of histiocytes in the dermis. In some examples, the mucinosis is associated with elastolysis (S5C12P6-4). Some examples of LE are manifested in cutaneous lesions which are rich in dermal mucopolysaccharides (such lesions might be characterized as LE mucinosis) (S5C16P10-3-6, & S5C17P11-3 & 4; the mucinous changes might even contribute tumoral qualities (LE tumidus).

Dermal mucinosis in lesions of LE may be associated with mucinous changes in the subcutaneous fat. If these changes are purely mucinous, they are acceptable as a rather extensive form of LE mucinosis. On the other hand, involvement of the subcutaneous fat in such a manner may be evidence of an early stage in the evolution of lupus profundus (panniculitis). Fibrin tends to deposit in mucinous zones (the deposits qualify as fibrinoid). If a zone of fibrinoid degeneration undergoes organization, the end-result is a deposit of hyalin (hyalinosis). Hyalin may undergo necrosis and then may calcify.

Dermal fibrosis is a feature of some lesions of LE, particularly old, long-standing lesions (S5C12P6-5-7).

Occasionally, in lesions of LS&A, the patterns of a cell-rich (lichen planus-like) reaction focally are represented. In these cell-rich components, the papillary dermis may not be significantly hyalinized; there may be prominent patterns of basement membrane hyalinosis (S5C12a P6a-1-6). These basement membrane changes may represent the incipient stage of a variant of hyalinosis. The basement membrane changes may be confused with changes seen in lesions of LE.

Colloid bodies (rounded, acidophilic bodies, often with a central rounded defect) are necrotic keratinocytes which come to lie in the papillary dermis in association with lichenoid reactions. They are not a prominent feature of the common forms of LE but may be a feature of the LP-LE overlap syndrome.

Lytic defects at the dermal-epidermal interface which contain clusters of colloid bodies are a lichen planus-like feature. If encountered in a lesion in the immunologic setting of LE, the finding should suggest the possibility of LP-LE overlap syndrome (S5C13P7-1-2).

Some newborns of some mothers with LE develop a cutaneous eruption that has lichenoid qualities (S5C13P7-3-5). This disease, neonatal lupus, is thought to be secondary to transplacental transfer of auto-antibodies.

The follicular component of LE is erosive, mostly above the level of the isthmus. As the changes in follicles progress, the follicular epithelium undergoes atrophy, primarily of the basal unit. The epithelium of an affected follicle may persist for a time as a thin superficial unit. For such a follicle, the normal extrusion of follicular contents to the surface tends to be impeded. As a result, the follicular lumen enlarges; in such a lumen, keratinized debris will collect (abnormal debris produced by abnormal follicular epithelium) (S5C16P10-1); such follicles are ectatic (patulous) and the contents are spoken of as follicular plugs. Whether the process induces catagen involution or interferes with subsequent anagen progressions (S5C17P11-1), the end-result is  an arrested follicle that eventually loses it right of domain in the dermis; it permanently regresses (undergoes atrophy), and in the process leaves behind a widened, fibrotic sheath (S5C13P7-6) (perifollicular sclerosis has a role in the atrophy of follicles; the vertically oriented scar becomes a marker for a common end-stage pattern, alopecia cicatrisata). The tracts of fibrous tissue are markers for sites in which follicles have undergone atrophy. Characteristically, the scarring alopecia of LE is additionally distinguished by effacement of the rete patterns at the dermal-epidermal interface (liquefaction degeneration may not be represented at the D-E interface in long-standing lesions).

The changes in the epidermis of a lesion of subacute lupus erythematosus are of a type which might be characterized as erythema multiforme-like. Occasionally, an erythema multiforme-like disease complicates LE (S5C13P7-7-10); perhaps, such examples are a variant of subacute LE.

A biopsy of a lesion of hypertrophic LE may be confused with squamous cell carcinoma (S5C14P8-1).

Sweat ducts may also be involved by the lichenoid reaction in lesions of LE (S5C14P8-2-3). The follicular changes occasionally are cell-poor (S5C15P9-3)

Some examples of LE are characterized by epidermal atrophy, a paucity of inflammatory infiltrates, and dermal atrophy with mucinosis (S5C14P8-4-5). For lesions showing this combination of changes, dermatomyositis also should be considered in the differential diagnosis.

Perivascular hyalinosis is often a feature of lesions of DLE (S5C15P9-2).

In some examples of LE, particularly lesions of the scalp, the dermis is fibrotic and the changes resemble those of superficial morphea (sclerodermoid LE) (S5C15P9-4-6).