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Epidermolysis Bullosa Acquisita (tier 2)
Epidermolysis bullosa acquisita
is an immune-mediated, sub-epidermal, vesiculo-bullous disease. It is characterized by deposits of IgG and complement in peri-lesional skin; the immune deposits are linear in the patterns of bullous pemphigoid. In contrast to pemphigoid, the deposits are localized to the fibrillary, sub-lamina densa region of the dermal-epidermal junction. In keeping with anatomic distinctions, the EBA antigen is different from that of bullous pemphigoid (BP). The clinical presentation resembles that of BP. Some examples clinically are non-inflammatory and some are inflammatory. Indirect immunofluorescence of saline-split skin is emphasized as a technique which is an aid in making a distinction between EBA and BP. With a characterization, in such detail, of an immune-mediated disease, it is difficult to understand the unwillingness of clinicians to find some category, other than epidermolysis bullosa, for this distinctive disorder. Some of the cases, in their clinical presentation, are associated with dystrophic changes, including scarring and milia.
The epidermis over a lesion of EBA often shows hyperplasia (S6C32P26-1), but this
quality may be a consequence of the sites commonly involved, and thus selected, for biopsy. The bulla is sub-epidermal. At the margins of the defect, the angle between the roof and the floor is fairly acute (most of
the lesions will have been ruptured at the time of biopsy). Just beyond the angle, and away from the bulla, supra-papillary clefting is a feature; a defect forms at the tips of neighboring dermal papillae, while the
extremity of the respective rete ridges remain attached to the papillary dermis (S6C32P26-1 & 8, S6C33P27-2-4, & S6C34bP28b-2, 4, & 6).
In some lesions (apparently early lesions), the papillary dermis shows lysis of connective tissue, particularly in the dermal papillae, with activation of connective
tissue cells (S6C32P26-6 & 7, S6C33P27-1, S6C34aP28a-1, & S6C34bP28b-8).
In older lesions, the papillary dermis is widened and fibrotic (S6C32P26-2-4, S6C33P27-3-6, S6C34aP28a-2, & S6C34bP28b-1-7). Vessels are ectatic. At the interface between the papillary dermis and the reticular dermis,
some of the lesions show perivascular infiltrates of lymphoid cells; the infiltrates follow vessels into the papillary dermis (S6C32P26-1 & 2).
Most of the lesions show a papillary dermis that is remarkably free of lymphoid cells. Along the floor of the defect, and within the defects, some of the lesions show infiltrates of activated histiocytes (S6C32P26-4 & 8, & S6C33P27-3 & 4).
One example, from the selected cases, shows a distinctively different pattern (S6C34P28-1 & 2).
Either this is an exceptional example, or the clinical impression (along with whatever laboratory work influenced this impression) was inaccurate. The other cases are remarkably similar; variations appear to be
related to the age of lesions at the time of biopsy.
Drug Eruption
Subepidermal bullae may be encountered in the setting of drug eruptions. A distinctive bullous disorder may be seen in the setting of a reaction to
barbiturates. It is cell-poor and subepidermal. In the chosen example, the superficial unit of the epidermis focally is necrotic, but the basal unit of the epidermis is hyperplastic. A distinguishing feature is the
necrosis of sweat glands (S6C36P30-1-4).
Neurotic Excoriation
The “neurotic excoriation” has been discussed in the section on Vasculitides. An example, late in its evolution, may show what appears to be a subepidermal defect containing degenerating acute inflammatory cells (S6C36P30-5); the lesion might be mistaken for an inspissated vesicle, or pustule. The defect is actually a result of lysis of necrotic
dermal tissue at its interface with viable connective tissue. The lysis is mediated at the level of infiltrates of neutrophils. The roof of the defect consists of not only necrotic epidermis, but also of a portion
of necrotic papillary dermis. It may include a thin layer of necrotic reticular dermis (S6C36P30-6). In the example, epidermis has
partially regenerated along the floor of the defect (S6C36P30-7); the roof of the defect is a sequestrum.
Porphyria
The histologic features of cutaneous lesions of porphyria cutanea tarda
approach a state of uniqueness. Quite part from the disease process, the histologic features of the commonly affected site, and thus the site most likely to be selected for biopsy, provides some of the uniqueness. The histologic specimen, with rare exception, presents the features of acral skin; the qualities of acral skin should be kept in mind when puzzling over the nature of a sub-epidermal vesicle that is remarkably cell-poor and, additionally, is distinguished by the preservation of elongated dermal papillae along the floor of the defect. Such a lesion, with few exceptions, will prove to be a marker for porphyria. In addition, some examples will show hyalinization of epidermal basement membrane bordering the vesicle. Some also will show hyalinization of the walls of vessels in the upper portion of the dermis. The vascular and basement membrane changes are related to the presence of deposits of immunoglobulins and complement. The vascular alterations may impart a stiffness to the vessels that in turn serves as scaffolding and, in turn, provides support for the respective dermal papillae. In this manner, the papillae project into the defect in a manner that has been characterized as “festooning.”
Not all the lesions in the setting of porphyria are acral and vesicular, or bullous. Some of the changes have been characterized as sclerodermoid. Some of the
fibrosing changes may be truly sclerodermoid; they may resemble those of scleroderma. Some are more distinctive and seem to be more in the nature of sclerosis of the adventitial dermis with extension of the
fibrosing process into the upper portion of the reticular dermis. Alopecia has been reported in association with porphyria. Lupus erythematosus also has been seen in association with porphyria.
Lim HW, Poh-Fitzpatrick: Hepatoerythropoitic porphyria: a variant of childhood-onset porphyria cutanea tarda. J Am Acad Dermatol 1984;11: 1103-11.
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