Pemphigus foliaceus
Pemphigus foliaceus is an autoimmune blistering disease of the skin. Pemphigus foliaceus causes a characteristic inflammatory attack at the subcorneal layer of epidermis, which results in skin lesions that are scaly or crusted erosions with an erythematous base. Mucosal involvement is absent even with widespread disease.
If there is an autoimmune IgG buildup in the epidermis, then nearly all of the antibodies are aimed against desmoglein 1. The effect of the antibodies and the immunological pathway is most likely one of three mechanisms:
- Steric hindrance of the desmoglein 1: The antibody caps off the site for intracellular binding to another keratinocyte.
- Activation of an endocytic pathway: The antibody activates a pathway which causes an internalization of desmogleïn 1, which in turn causes a loss of adhesion.
- Disruption of function: In this case, the antibody blocks the desmoglein 1 from being formed into a desmosome. This in turn causes a loss of adhesion with acantholysis as a result.
Cause
The National Institute of Arthritis and Musculoskeletal and Skin Diseases describes the disease thus:Signs and symptoms
The characteristic lesions are crusted, scaly erosions on an erythematous base. In more localized and early disease, lesions are well demarcated and have seborrheic distribution. Small flaccid vesicles, unlike pemphigus vulgaris, are not found. The disease may develop slowly or may rapidly progress, resulting in an exfoliative erythroderma. UV radiation exacerbates pemphigus foliaceus. Patients experience burning and pain. The colloquial term for Brazilian endemic pemphigus, fogo selvagem and for the rare Hungarian variant, Csíp mint az erős Pista, takes into account many of the clinical aspects of this disease: the burning feeling of the skin, the exacerbation of disease by the sun, and the crusted lesions that make the patients appear as if they had been burned.Diagnosis
Pemphigus foliaceus is diagnosed base on history, biopsy of the affected skin, and testing either a blood sample or a skin sample for the antibodies that cause pemphigus.The differential diagnosis includes other forms of pemphigus, bullous impetigo, subcorneal pustular dermatosis, subacute cutaneous LE, and seborrheic dermatitis. As discussed earlier, the demonstration of IgG autoantibodies against epidermal cell surfaces is essential for separating these disorders from the pemphigus family. A complete review of medications should be done to exclude the possibility of drug-induced pemphigus foliaceus. Because the lesions of pemphigus foliaceus may become secondarily infected, the finding of bacteria does not confirm a diagnosis of bullous impetigo. Likewise, a clinical flare or recalcitrant disease may represent a superimposed disorder, e.g. tinea corporis, especially in patients on systemic corticosteroids.