Epidermolysis bullosa acquisita (EBA) is an autoimmune blistering disease characterized by autoantibodies to type VII (anchoring fibril) collagen. Therefore, it is a prototypic autoimmune disease defined by a well-known autoantigen and autoantibody. In this study, we injected hairless immune competent mice with purified immunoglobulin G (IgG) fraction of serum from rabbits immunized with the non-collagenous amino-terminal domain (NC1) of human type VII collagen, the domain known to contain immunodominant epitopes. As a control, identical mice were injected with the IgG fraction of serum from non-immunized rabbits. Mice injected with immune IgG developed subepidermal skin blisters and erosions, IgG deposits at the epidermal-dermal junction of their skin, and circulating anti-NC1 antibodies in their serum-all features reminiscent of patients with EBA. Similar concentrations of control IgG purified from normal rabbits did not induce disease in the mice. These findings strongly suggest that autoantibodies that recognize human type VII collagen in EBA are pathogenic. This murine model, with features similar to the clinical, histological, and immunological features of EBA, will be useful for the fine dissection of immunopathogenic mechanisms in EBA and for the development of new therapeutic interventions.

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Acquired reactive perforating collagenosis (ARPC) is an uncommon dermatosis characterized by transepidermal elimination of altered collagen. It is commonly seen in patients with diabetes mellitus and/or chronic renal insufficiency. Rarely, it has been reported in association with malignancy and other conditions. We report a 30-year-old woman with insulin-dependent diabetes mellitus who presented with multiple, discrete, violaceous, hyperkeratotic papules on the extensor aspects of both legs, characteristic of ARPC. Four months later, metastatic papillary thyroid cancer was diagnosed. This case further supports the possibility that ARPC may represent a paraneoplastic phenomenon.

Botryomycosis is an uncommon, chronic, granulomatous and/or suppurative, opportunistic infection affecting the skin and viscera, primarily caused by bacteria. The exact pathogenesis of this infection is not well understood. However, both the host's immune status and microbial infectivity have been implicated in the pathogenesis of this unusual clinical condition. To date, botryomycosis caused by a nonbacterial pathogen has not been reported in the literature. We report a case of cutaneous botryomycosis caused by combined Staphylococcus aureus and Pneumocystis carinii. Cutaneous P. carinii infection without pulmonary involvement is extremely rare.

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