Drug exanthema maculo-papular L27.0

Most frequent cutaneous adverse drug reaction, which can probably be classified as type B of cutaneous drug-induced reactions (type B reactions are apparently partly independent of the dose and cannot be predicted due to the pharmacological property of the drug) In most maculo-papular drug exanthema there is a specific reaction of the immune system (immunoglobulins, T cells) against the drug or its metabolites.

According to the classification of Coombs and Gell, drug exanthema is an allergic reaction of type IV (late type allergic reaction). In most cases this is a specific reaction of the immune system against a drug or its metabolites, often occurring in combination with a "common" infection. Activated T cells as well as basal keratinocytes and endothelial cells express various activation markers as well as co-stimulatory molecules and adhesion molecules such as HLA DR (MHC class II molecules), CD11a, CD18 (LFA-1), CD62L (L-selectin) and CD54 (ICAM-1). In addition, type I cytokines such as INF-gamma and type II cytokines such as IL-5 are produced. The increased production of IL-5 as well as eotaxin (CCL-11) offers an explanation for eosinophilia, which is typically present in these drug allergies.

The skin symptoms usually occur between the 7th and 12th day after the start of therapy, but also after several weeks or after discontinuation of the drug. In patients who are already hypersensitive, immediate reactions (immediate to 60 minutes) or delayed reactions (>1 hour to several weeks) may occur. This may manifest as flushing, urticaria, angioedema, bronchospasm, or anaphylaxis.

Generalized, truncal and extremity, variably dense exanthema with red spots, patches, papules, and plaques. Usually accompanied by pruritus (pruritus may be completely absent). Depending on the size and type of efflorescences, the exanthema is also called: rubeoliform, scarlatiniform, morbilliform, psoriasiform or lichenoid, among others. A topographical variant is the so-called baboon syndrome (also called SDRIVE).

• Histology: Superficial mixed cell infiltrate, typically interfacial dermatitis with vacuolisation of the basement membrane zone and single cell necrosis.
• Immunohistology: In the infiltrate CD3+ T-cells predominate; CD4+ > CD8+ cells (see in contrast: drug exanthema, bullous).

• Stopping the triggering medication.
• Depending on the clinical symptoms, treatment with systemic glucocorticoids: initial prednisolone 50-150 mg/day p.o./i.v., then reduce the dose as the disease progresses.